RadGridView cannot resolve the proper filtering values as the declaratin type of the DataTable column is Position, but it really contains numeric values. You can set the column's DataType to be int, which is the actual type of the bound values. Then the distinct value will be loaded as numerics. If you want to modify the way in which they are displayed, you can modify RadGridVIew FilteringControl's template.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items