Aviat 617 flight computer

[Spir4]

Hello,

I was looking at the Aviat 617 flight computer, but I've noticed there are a couple of different versions with different scales:
A-B 60-350/100-500 Scale Flight
A-G 60-350/300-1000 Scale Flight
A-K 60-350/150-750 Scale Flight
B-H 60-B-H 100-500/40-250 Scale Flight

Does any one know what those scales mean? I've googled it quite a bit, but no results.

Thanks!