However I'm writing with quite a lot of ignorance on my part <grin>. Is the 620 a relatively new device and possibly you still use the old Garmin Connect site and Garmin Communicator does not work with the 620? If that's the case you can likely manually upload the file to the old Garmin Connect. Garmin Express is supposed to put a copy of it on your PC/Mac, where I don't know, but the question/answer probably is already in a post to the Garmin Express subforum.
The units you display on your device are controlled by settings on your device. The units you display on Garmin Connect or other sites is usually controlled by the settings associated with your user profile on that site.
