Group totals are at the end of the page instead of after the group and are "NaN".

Hi, I wand to group on the first column and total the last three columns. I used the example provided however the totals appear at the end of the page instead of after the group and are "NaN". Also, is it possible to only provide a total at the end of a group and not when a group finishes at the end of a page (i.e., if a group goes over three pages have one total at the end)?

The code is (I tried with rowGroup first):

 var activityUpdateTable = $('#activityUpdateTable').DataTable( {

        "info":     false,
        dom: 'Bfrtip',
        buttons: ['copy', 'csv', 'excel', 'pdf', 'print'],
        columns: [                  
              { data: null, render: function ( data, type, row ) {
                  // Combine the first and last names into a single table field
                  return data.surname+', '+data.firstname;
              } },
              {data: 'startDate',
                  defaultContent: ""},
              {data: 'type',
                  defaultContent: ""},
              {data: 'description',
                  defaultContent: ""},
              {data: 'kilometres',
                  defaultContent: "0"},
              {data: 'nightsUnderCanvas',
                  defaultContent: "0",
              },
              {data: 'nightsInBuilding',
                  defaultContent: "0",
              },
             ],
         columnDefs: [ {
             targets: [1],
             render: $.fn.dataTable.render.moment( 'DD/MM/YYYY' )
         } ],

         rowGroup: {
            startRender: null,
            endRender: function ( rows, group ) {
                var kmTotal = rows
                    .data()
                    .pluck(4)
                    .reduce( function (a, b) {
                        return a + b*1;
                    }, 0);

                var canvasTotal = rows
                    .data()
                    .pluck(5)
                    .reduce( function (a, b) {
                        return a + b*1;
                    }, 0);

                var buildingTotal = rows
                 .data()
                 .pluck(6)
                 .reduce( function (a, b) {
                     return a + b*1;
                 }, 0);

                return $('<tr/>')
                    .append( '<td colspan="4">Totals:</td>' )
                    .append( '<td>'+kmTotal+'</td>' )
                    .append( '<td>'+canvasTotal+'</td>' )
                    .append( '<td>'+buildingTotal+'</td>' );
            },
            dataSrc: 0
        },
    } );