How to define grid aggregates using data attribute, with below, its always display "Total Count: 0" 
<script id="fooTemplate" type="text/x-kendo-template">    <div id="foo_details">        <div data-role="grid"             data-groupable="true"             data-scrollable="true"             data-pageable="true"             data-reorderable="true"             data-resizable="true"             data-sortable="true"             data-filterable="true"             data-columnMenu="true"             data-columns='[                                 { "field": "caseNumber", "title": "Numer sprawy", "aggregates": ["count"], "footerTemplate": "Total Count: #=data.caseNumber? data.caseNumber.count: 0#" },                              ]'             data-bind="source: details"             style="height: 400px"></div>        <script>          var viewModel = kendo.observable({            details: new kendo.data.DataSource({              transport: {                read: {                  url: API_URL + 'foo',                  dataType: "json",                },              },              aggregate: [                {field: "caseNumber", aggregate: "count"},              ],            }),          })          kendo.bind($('\#foo_details'), viewModel)</script></div></script>