Apply Levels defined

If that option is set to "Yes", the levels defined in the Cross Table or the cube will be displayed as if the cross table or the cube had been generated, taking care about the Hide detail and the Show detail levels.

If that option is set to "No", the report will not take care about the levels defined in the Cross Table or the cube and will display all the levels as if the Show detail was applied to all the levels and sub-levels.