There are a few reasons why this might be happening:

You are receiving files from other peers that are not required.  Sometimes incoming data does not match what you requested, so the files are discarded.  This is also known as wasted data, and it is common.

Seeding can also lead to more data consumption than is contained in the file you downloaded.  If you would like to reduce your data consumption, you can pause seeding on one or more torrents.  Tap on the toggle next to the torrents you would like to pause. To pause all torrents, tap on the menu button (three dots) in upper corner of the screen in portrait (vertical) mode.  Tap ’Pause All.’.  Note that some Samsung devices will have the menu button in the lower right corner of the phone, not on the actual screen.