I assume you have a manual. The only thing I can think of for GND is ground. About 30 pages in, the manual shows how to connect the cabinet to electrical and the GROUND lug. Don't be overly concerned) unless you plan on making this permanent.

I'm using the NO308 rev J or higher practice and it says that only 10 and 17 were programmed for all ring. It's program 50 and you should be able to dial 11, press lines A1, A2, etc, then # and dial 12, press lines A1, A2 until you're done. Finish with *

Carl