Kendo Grid Aggregates

Kendo Grid Aggregates behaves weirly when virtualization is activated

HTML

<!DOCTYPE html>
<html>
<head>
    <base href="https://demos.telerik.com/kendo-ui/grid/column-virtualization">
    <style>html { font-size: 14px; font-family: Arial, Helvetica, sans-serif; }</style>
    <title></title>
    <link rel="stylesheet" href="https://kendo.cdn.telerik.com/2022.2.802/styles/kendo.default-ocean-blue.min.css" />

    <script src="https://kendo.cdn.telerik.com/2022.2.802/js/jquery.min.js"></script>
   
    <script src="https://kendo.cdn.telerik.com/2022.2.802/js/kendo.all.min.js"></script>


</head>
<body>
    <div id="example">
    <div id="grid"></div>
 
</div>



</body>
</html>

JavaScript

$(function() {
            let columns = [];
            let data = [];
            let numberOfColumns = 15;
            let numberOfRows = 35;
            let row, field, groupable, groupableTemplate, props;
               
            for (let i = 1; i <= numberOfColumns; i++) {
                field = ("Field" + i);
                groupable = false;
                groupableTemplate = null;
              	props = { field: field, title: field, width: 200 };
                
              	if(i == 6) {
                	groupableTemplate = `Total : #: data['${field}'] ? data['${field}'].count : 0 #`;
                  groupable = true;
                 }
                 
                 if(i == 8) {
                	groupableTemplate = `Sum : #: data['${field}'] ? data['${field}'].sum : 0 #`;
                  groupable = true;
                 }
              
              	props.groupFooterTemplate = groupableTemplate; 
                props.groupable = groupable;
                
                columns.push(props);
            }
            
            // --- --- ---
            
            let val;
            for (let i = 1; i <= numberOfRows; i++) {
                row = {};
                
                for (let j = 1; j <= numberOfColumns; j++) {
                    field = ("Field" + j);
                  	val = null;
                   	
                  	if(j == 6)
                      val = 1;
                  	else if (j == 8)
                      val = 2;
                  	else
                      val = "R" + i + ":C" + j;
                  
                    row[field] = val;
                }
                
                data.push(row);
            }

           var dataSource = new kendo.data.DataSource({
               pageSize: 10,
               data: data,
               group: [
               	{ field: "Field6", aggregates: [ { field: "Field6", aggregate: "count" }, { field: "Field8", aggregate: "sum" } ] },
        ...