Storage Apps more than 800 GB on 256 GB SSD
Although the issue I see normally is with "Backups" growing to ridiculous sizes, it's possible this issue is a variant of the same problem... Try typing sudo tmutil disablelocal into the Terminal and enter your password, then turn Time Machine off and on,. If this is the same issue, in a minute or two the numbers should return to normal.

What this does is it disables local time machine backups, which are occasionally useful if you don't backup often, or if you don't have access to your backup drive for an extended period of time, and would like to restore a recently modified document. It often bugs out in various ways.