I built a custom class and method to return the aggregate data to plot a chart using LWC.  For the purpose of example, I hardcode the AccountId for now.

public with sharing class lwcLifetimeSpendingController {
    @AuraEnabled (cacheable=true)
    public static List<AggregateResult> getAccountLifetimeSpending(){
        return [SELECT SUM(Service_Amount__c) Service, SUM(Subscription_Booking__c) Subscription  FROM Opportunity WHERE accountid = '0018000001G9dZUAAZ' and isclosed=true and iswon=true];
    }
}

Here's my JS file.  How do I retrieve the aggregate values from the custom apex controller and use in the JS?  I tried getSObjectValue, but that did not work as it worked only with field data from the return Object.

import { LightningElement,track,wire } from 'lwc';
import { getSObjectValue } from '@salesforce/apex';
import { loadScript } from 'lightning/platformResourceLoader';
import chartjs from '@salesforce/resourceUrl/chart';
import getAccountLifetimeSpending from '@salesforce/apex/lwcLifetimeSpendingController.getAccountLifetimeSpending';

const generateRandomNumber = () => {
    return Math.round(Math.random() * 100);
};

export default class LifetimeSpending extends LightningElement {    
    @wire(getAccountLifetimeSpending) lifetimeAggregateResult;
    @track error;
    
     //getSObjectValue does not work in this scenario
} //end export

Here's the sample of the HTML file

<template>
    <lightning-card title="Lifetime Spending" icon-name="custom:custom19">
        <div class="slds-m-around_medium">
            <canvas class="donut" lwc:dom="manual"></canvas>
        </div>
        <template if:true={error}>
            <c-error-panel errors={error}></c-error-panel>
        </template>    
    </lightning-card>
</template>