I have a wrapper class that iterate. I want to get the vlaue of just one text field from the iteration. That field is used to create a new record for a different object. 
Lightning component

<aura:component controller="billDownCtrl" Implements="flexipage:availableForRecordHome, force:lightningQuickActionWithoutHeader">
	<!-- Attributes and handlers-->
    <aura:attribute name="venList" type='billDownCtrl.wrapper[]'/>
    <aura:handler name="init" action="{!c.doInIt}" value="{!this}" />
    <aura:attribute name="venId" type='string'/>
    <aura:attribute name="amt" type="Decimal"/>
    <aura:attribute name="amtList" type="Decimal[]"/>
    
    <lightning:card title="Download Cycle ">
       
    <section >
          <table class="slds-table slds-table--bordered slds-table--striped slds-table--cell-buffer " role="grid">
  
              <!--Display the bill download cycle -->
              			<tbody>
              <aura:iteration items="{!v.venList}" var="ven" indexVar="rowIndex">
    		 <tr>
                    <th scope="row" data-index="{!rowIndex}" >
                        <lightning:formattedNumber value="{!ven.down}" /></th>
                  </tr>
   			 
                            
                           
                           
 			<table class="slds-table slds-table--bordered slds-table--striped slds-table--cell-buffer ">
                   		                        
                		<aura:iteration items="{!ven.acc}" var="eng" >           
                            	  <thead>          
           								 <tr class="slds-text-body_small" role="gridcell"> 
             		   <th scope="col" style="width:50px"><span class="slds-truncate" role="gridcell">Portal Link</span></th>
                                  										</tr>
       										 </thead>
                            
        <tbody>
            <lightning:formattedText linkify="true" value="{!eng.Portal_Link__c}" /> <br/>
            
           					
            							<!--Display vendor invoices -->
          <table class="slds-table slds-table--bordered slds-table--striped slds-table--cell-buffer ">
                   			            
           						<thead>          
            <tr class="slds-text-heading--small"> 
                <th scope="col"><span class="slds-truncate">Vendor Invoice</span></th>
                <th scope="col"><span class="slds-truncate">Customer</span></th>
                <th scope="col"><span class="slds-truncate">Login</span></th>
                <th scope="col"><span class="slds-truncate">Password</span></th>
                <th scope="col"><span class="slds-truncate">Last Download</span></th>
                <th scope="col"><span class="slds-truncate">Location Name</span></th>
                <th scope="col"><span class="slds-truncate">Location Address</span></th>
                <th scope="col"><span class="slds-truncate">Bill Cycle</span></th>
                <th scope="col"><span class="slds-truncate">Current Amt Due</span></th>
                <th scope="col"><span class="slds-truncate">Completed</span></th>
            </tr>
            
        </thead>
       										 
										<aura:iteration items="{!eng.Vendor_Invoices__r}" var="ac">                                                          
        <tbody>
            
                 <!--Form for the vendor invoices -->    
            
            <tr>
                  
                            <td>
  <th scope="row"><a href="{!'/one/one.app?#/sObject/'+ ac.Id + '/view'}"> <lightning:formattedText value="{!ac.Name}" /></a></th>
                             </td>
                            <td>
                                <lightning:formattedText value="{!ac.Account__r.Name}" />
                            </td>
                        <td>
                            <lightning:formattedText value="{!ac.Login__c}" /> <br/>
                            <lightning:button iconName="utility:copy_to_clipboard"
                          onclick="{!c.copyInputFieldValue}"
                          label="Copy"
                          value="{!ac.Login__c}"/>
                            </td>
                            
                            <td>
                                <lightning:formattedText value="{!ac.Password__c}" /> <br />
                                <lightning:button iconName="utility:copy_to_clipboard"
                          onclick="{!c.copyInputFieldValue}"
                          label="Copy"
                          value="{!ac.Password__c}"/>
                             </td>
                            <td>
                                 <lightning:formattedDateTime value="{!ac.Last_Download__c}" />
                             </td>
                            
                            <td>
                                <lightning:formattedText value="{!ac.Location_Name__c}" />
                            </td>
                            
                		  <td>
                                <lightning:formattedText value="{!ac.Location_Address__c}" />
                            </td>
                			
                  			<td>
                                <lightning:formattedNumber value="{!ac.Bill_Cycle__c}" />
                                
                            </td>
                <td><lightning:input type="number" aur:id="amtList" value="{!ac.Data_Bill_Benchmark__c}" name="{!rowIndex}" onchange="{!c.getAmt}"/></td>
                
        <td><button type="button" onclick="{!c.complete}" name="{!rowIndex}" class="slds-button slds-button--brand" id="{!ac.Id}">Completed</button></td>
            </tr>
                            </tbody>
              </aura:iteration>           
                                    </table>
                                
        </tbody>
         </aura:iteration>    
    </table>
                                    <!-- End of displaying Vendor Invoice-->
                            
                  
                            </aura:iteration>
              						</tbody>
        								</table>
           		 </section>
        
    </lightning:card>
</aura:component>

JS Controller:

getAmt : function(component, event){
         var amtlist = component.find('amtList').get('v.value');
            var getIndex = event.getSource().get("v.name");
		        var form = component.get("v.venList");
      		 var amt = form[getIndex];
        alert(amt.amtlist);
        component.set('v.amt', '');

    },

Any help would be appreciated