I'm still trying to figure out what it's actually reading from the screen (if anything).....
Basically it is the serial number of theWatch. It is just a neat type of a bar code.
How do you know this? It probably is, but do you have a source with detail of how it works?
If it is the serial I guess that would make sense. The watch would transmit its serial over BT. As there could be multiple watches in this state then pointing your phone at the screen and getting the serial would then let the phone determine which of the multiple serial numbers it can detect is the one with which to pair.
Basically it is the serial number of theWatch. It is just a neat type of a bar code.