<apex:page controller="CASReportController">
    <apex:form >
        <apex:pageBlock title="JSON Deserialized Response">
            <apex:pageBlockButtons >
                <apex:commandButton value="submit" action="{!deserialize}" reRender="DealerBlock"/>
            </apex:pageBlockButtons>


            <apex:pageBlockSection id="DealerBlock" columns="1">
                <apex:repeat value="{!wrapper}" var="cap1">

                    <apex:pageBlockTable value="{!cap1.caPerformanceRecordList}" var="cap" width="100%">

                        <apex:column headerValue="Reporting Period" value="{!cap.reportingPeriod}"/>

                        <apex:column headerValue="FS Integration Type Code" value="{!cap.financeSourceIntegrationTypeCode}"/>

                        <apex:column headerValue="IDL Plus" value="{!cap.idlPlus}"/>

                        <apex:column headerValue="Credit Application Source Code" value="{!cap.creditApplicationSourceCode}"/>

                        <apex:column headerValue="Submission Count" value="{!cap.submissionCount}" />


                        <!-- Generating CASubmissionCount total -->



                        <!--footer of the SubmissionCount -->
                        <apex:facet name="footer">
                            Total Count: <span class="t1" style="pading-left:20px"> </span>   {!cap1.appTotal}               <b><!--  expecting Total Count = 7 --    submissionCount of one record is 2 and other record is 7 as seen in json string -->    </b>
                        </apex:facet>

                    </apex:pageBlockTable>
                </apex:repeat>

            </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:form>
</apex:page>

-------------- Apex Controller------- -----
public with sharing class CASReportController {
    @AuraEnabled
    public list<JSONWrapperController> wrapper {get;set;}

    public void deserialize() {

        try{
            string jsonresponse = '[{ "caPerformanceRecordList": [ { "motorDealerID": "XL1HX", "dealerName": "Subaru Auto Dealer", "reportingPeriod": "2019-05-18", "financeSourceIntegrationTypeCode": "FIFS", "idlPlus": "Y", "creditApplicationSourceCode": "STEONE", "submissionCount": 2 }, { "motorDealerID": "XL1HX", "dealerName": "Subaru Auto Dealer", "reportingPeriod": "2019-06-27", "financeSourceIntegrationTypeCode": "FIFS", "idlPlus": "Y", "creditApplicationSourceCode": "STEONE", "submissionCount": 5 } ], "ecPerformanceRecordList": [ { "motorDealerID": "XL1HX", "submitUserID": "BCUSER1", "bookedDate": "2019-05-22 00:00:00.0", "ecEligible": "Y", "caBookedCount": 1, "ecBookedCount": 0 }, { "motorDealerID": "XL1HX", "submitUserID": "BCUSER1", "bookedDate": "2019-06-05 00:00:00.0", "ecEligible": "Y", "caBookedCount": 1, "ecBookedCount": 0 } ] }]';

            system.debug('json string is ' +jsonresponse);
            wrapper = (list<JSONWrapperController>) JSON.deserialize(jsonresponse, list<JSONWrapperController>.class);

            getTotalAppCount(wrapper);
            system.debug('This is the wrapper class: ' +wrapper);
        } catch (Exception e){
            system.debug('Error---->' +  e.getLineNumber() + e.getMessage());

        }
    }


    public void getTotalAppCount(list<JSONWrapperController> wrapper) {
        // loop through each element in the     caPerformanceRecordList, till the end of the list.
        // get grand total of submissionCount
        // return grand total


        for(JSONWrapperController jw: wrapper){
            jw.appTotal=0;
            for (CaPerformanceRecordList cp : jw.caPerformanceRecordList) {
                jw.appTotal += cp.submissionCount;
            }
        }

    }


public class JSONWrapperController {

public List < CaPerformanceRecordList > caPerformanceRecordList{
get;set;
}
public List < EcPerformanceRecordList > ecPerformanceRecordList{
get;set;
}
    public  integer appTotal{get;set;}

}
public class EcPerformanceRecordList {
public String motorDealerID{get;set;}
public String submitUserID{get;set;}
public String bookedDate{get;set;}
public String ecEligible{get;set;}
public Integer caBookedCount{get;set;}
public Integer ecBookedCount{get;set;}
}



public class CaPerformanceRecordList {
public String motorDealerID{get;set;}
public String dealerName{get;set;}
public String reportingPeriod{get;set;}
public String financeSourceIntegrationTypeCode{get;set;}
public String idlPlus{get;set;}
public String creditApplicationSourceCode{get;set;}
    public Integer submissionCount{get;set;}

}

}