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.

If you would like to reduce your data consumption, you can pause seeding on one or more torrents.  Tap on the toggles 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. 

When you’re back on wifi, you can resume seeding on all torrents by tapping on the menu button (three dots) in upper corner of the screen in portrait (vertical) mode.  Tap ‘Resume All.’ Or, you can resume one or more torrents by tapping on the toggles next to the torrents you would like to resume. Note that some Samsung devices will have the pause button (||) in the lower right corner of the phone, not on the actual screen.