Transmission using an abnormally large amount of bandwidth

[skittlebox]

I noticed today that Transmission has used up and abnormally large amount of my monthly bandwidth. I left a torrent running that had 500MB left. When I came back to it 200MB had finished and 90MB had been uploaded(Which is about average for my internet speed), but when I checked my monthly bandwidth(I have a small limit and monitor it closely so I don't go over) 800MB had been used in the session. No one else has access to the connection and nothing had been running but Transmission.

Even now Transmission is saying the torrent is downloading at 30kb/s and uploading at 10kb/s, but my airport card is reading in:59kb/s and out: 16kb/s. I'm not downloading anything else and Transmission is the only thing running. I can't figure out where all the extra bandwidth is coming from. Can anyone help me figure out why this is happening only when transmission is open?