Default Twrp nandroid backup small file size

I recently switched to using compressed backups because the 4 GB backups were filling up my internal storage.

Well... It worked better than expected. Much better. Now my backups take up 32 MB. Problem is: it sounds too good to be true. Either twrp uses an impressive compression algorithm or I have no idea how compression works for backups because quite frankly that sounds way too small to be able to restore anything.

Can anyone shed some light on this?

Sent from my LG-D802 using XDA Free mobile app

Edit: fixed it. Cleared all data and uninstalled then reinstalled online nandroid backup - no problems now.