When using FixedBottomItemCount and allowing Sorting, it messes up the list and the last two rows that was listed as Fixed at load is now within the sorted items. How can I avoid this?

In my case, I've created a Stored procedure that adds a summary and average row which is displayed in the fixed rows and I wish to keep those out from further sorting. Grid loads its data from a sqldatasource, which is using a stored procedure to load data from SQL and this data is sorted by a column named sortorder. You can access a sample here.

Is it possible to keep the sortorder column as a pimary sorting column and then the clicked column (name or month) as the secondary sorting so that the Total ans Average row is always the last two or is the behaviour with FixedBottomItemCount and sorting a bug that is fixed? I use version 9.0.15.2 of the eo.web.dll.