Hey @Krzysztof, using the "=" operator is not necessary to display the number of filtered objects. It can be achieved without it. Therefore, your assertion is incorrect.
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.8/angular.min.js"></script>
</head>
<body ng-app="myApp" ng-controller="myCtrl">
<p ng-repeat="x in people | orderBy: 'age'">{{x.name}},{{x.age}}</p>
<p>Total Filtered: {{people.length}}</p>
<script>
//Module declaration
var app = angular.module('myApp',[]);
//controller declaration
app.controller('myCtrl',function($scope,$timeout){
$scope.people = [{name:"Peter",age:15},{name:"Julie",age:28},{name:"Roger",age:17}];
});
</script>
</body>
</html>