Table Prefix used or not?

Hi,

The prefix can be changed, of course.

Have you checked this?
https://meowapps.com/media-cleaner-debug-issues/#2_Too_many_entries_are_detected_as_being_not-used

Are you sure your files aren’t used? They might actually be. What are the settings you are using?

I believe this was related to Media Cleaner “Non-Pro” version versus “Media Cleaner Pro can scan your physical /uploads directory”. Anyway… the problem is gone now.