It would appear that this is likely due to stopping and restarting torrents. See, your torrent client will show you the totals since your torrent was added to your torrent client. The tracker on the other hand will only show the data for the current session. When a session is stopped then restarted, this resets the data to zero.
The other factor is that your torrent client will only update with the tracker once every 30 minutes, and as such, there is a delay in the stats updating. If a session is stopped before the torrent client updates, usually any data that is transferred since the last update is lost.
Lastly, if you are seeding a torrent from more than one device or from more than one torrent client, this can cause many issues with the data being updated, as each torrent client will update appearing as a new session.