Time machine never stops first backup to NAS

Right before I upgrade to Lion my external HD I use to backup to with Time Machine died. So I got a new one, this one a NAS.

I got a Synology 211j, which claims to support Time Machine (TM). After I got it setup, I logged in and found that TM was all ready to back up to the NAS (it was a disk that I could select from the System Preferences, TM pane). I have a 250 GB HDD with 200 GB on it, TM claims I wanted to backup 147 GB after exclusions and then just kept backing up. It got to 200 GB when I had to disconnect it in the morning. Tonight I restarted it, it claimed it wanted 100 MB and now is rolling past a few GB.

Now, TM has backed up the HD, but the NAS and TM agree that the backup is taking up 200 GB. How is this possible? How do I know TM is actually doing what it claims?