12 years ago I put a post on this blog detailing how the keys were numbered on the 53xx range of IP Phones. I usually record these things in case I forget myself and maybe I help someone else along the way.
Recently putting 6930 phones on a Mitel MiVoice Business I found these don't follow the same pattern. The programing interface of the PBX has no picture of the phone with the buttons numbered so you have to figure it out from the thousands of pages of documentation. These phones make much more sense numbering from top to bottom with the left column first.
6930
1 7
2 8
3 9
4 10
5 11
6 12
All the best
John Rogers