Active Site Usage Not Matching Storage Used?

At my new position our SharePoint storage is getting used quickly.  As of right now we have 69GB available of 11.75TB.  When look at the active sites the total Storage Used only adds up to 2TB.  Where is the other 8.75TB coming from?  Version history was changed to 100 major versions and to delete versions after 1 year.  Is it possible that the versions still being retained could add up to 8.75TB?  I archived a site that was 13GB but it's still showing 69GB available.  How long does it take to reclaim that storage?