Simren's Quesiton

controllers.application.js

import Ember from 'ember';
const { computed } = Ember;

const Foo = Ember.Object.extend({
  init() {
    this._super(...arguments)
    this.set('amount', { value: 100 })
  },
  
  amountValue: computed.alias('amount.value')
})

const FOOS = [Foo.create(), Foo.create()]

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  init() {
    this._super(...arguments)
    this.set('item', { foos: FOOS })
  },
 
  
  totalNotWorking: computed('item.foos.@each.amount.value', function() {
    return this.item.foos.reduce((result, foo) => {
      return result + foo.amount.value
    }, 0)
	}),
  
  totalWorking: computed('item.foos.@each.amountValue', function() {
    return this.item.foos.reduce((result, foo) => {
      return result + foo.amount.value
    }, 0)
	}),
  
  actions: {
    incrementFirstsValue() {
      const firstItem = this.item.foos[0]
      Ember.set(firstItem, 'amountValue', firstItem.amountValue + 100)
    }
  }

});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
Total Not Working due to nested prop after @each: {{totalNotWorking}}<br>
<button onclick={{action "incrementFirstsValue"}}>Increment First Foo's Value</button><br>
Total Wirking: {{totalWorking}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}