[Solved] DataBinding(dataBinding => dataBinding.Ajax().Select question

[Max]

Hi all,
I am trying to understand the binding order process and how values are being passed.
If you look at the source code: http://demos.telerik.com/aspnet-mvc/razor/grid/selectionclientside?theme=vista
you will see in the line below that we are passing a parameter as "new":

        .DataBinding(dataBinding => dataBinding.Ajax().Select("_SelectionClientSide_Orders", "Grid", new { customerID = "ALFKI" }))

but we also have the following line: e.data = $.extend(e.data, { customerID: customerID });

Some situations if I remove the "new { customerID = "ALFKI" }", the parameter is still passed, and sometimes I get a null.
I am trying to understand when that is necessary. What is the co-relation between that "new" parameter with the Javascript call $.extend?

Code sample which I am refering to:

@(Html.Telerik().Grid((IEnumerable<Order>)ViewData["Orders"])
        .Name("Orders")
        .Columns(columns=>
        {
            columns.Bound(c => c.OrderID).Width(100);
            columns.Bound(c => c.OrderDate).Width(200).Format("{0:dd/MM/yyyy}");
            columns.Bound(c => c.ShipAddress);
            columns.Bound(c => c.ShipCity).Width(200);
        })
        .DataBinding(dataBinding => dataBinding.Ajax().Select("_SelectionClientSide_Orders", "Grid", new { customerID = "ALFKI" }))
        .ClientEvents(clientEvents => clientEvents.OnDataBinding("onDataBinding"))
        .Pageable()
        //.Pageable(paging => paging.PageSize(3))
        .Sortable()
)

<script type="text/javascript">
    var customerID;

    function onRowSelected(e) {
        var ordersGrid = $('#Orders').data('tGrid');
        customerID = e.row.cells[0].innerHTML;

        // update ui text
        $('#customerID').text(customerID);

        // rebind the related grid
        ordersGrid.rebind();
    }

    function onDataBinding(e) {
        e.data = $.extend(e.data, { customerID: customerID });
    }
</script>

Thank you!