“cases audit” is tracking the fields you tell it to track, in Studio / Cases / Fields, check the property Audit on each one.
Or maybe it’s easier to just to a Cases detail view (any one) and select from the action menu “View change log”
This will surely give you some clues about how it is piling up (probably useless) information.
If you don’t care about that information in Audit, I think you can just delete the rows from the table. However, you are the sole responsible for your data and I advise to have full backups and run this in a test environment first, so you can evaluate your decision to delete or not.