Here is some helpful information to know when sorting or filtering totals.
Casual users can edit existing sorts and filters on totals.
Advanced users and administrators can add new sorts and filters on totals and edit existing sorts and filters.
This feature is available on the Grand Totals that are on the same axis as the measure items. For example, the measures items in this view are in columns. The Grand Totals in columns can have sorts and filters applied to them.