Help!: Garmin GPS Routes Distance not in Sync with Garmin Stats

My Garmin 205 is uploading to the Garmin Software showing different distances as the MapMyRun site.

These distances are sometimes showing almost a KM difference. I tend to trust the Garmin results, but document my runs on this site which really affects my personal stats.

I mapped the linked route today (http://www.mapmyrun.com/run/canada/nb/moncton/259301859), the Garmin Distance is showing 10.35 KM. Map my run is importing it in as 9.95 KM. That is a 400m difference and is a little hard on my head. I also mapped my previous 1/2 Marathon (21 KM by the rule), but this one was imported as 20.7. Anyone have any suggestions as to why the import is showing these differences?