Lumia numbering, any logic?

I've always been wondering if there was any logic in the numbering of Lumia phones, it surely not as simple as higher the number better the phone. 950 and 950xl are the two top Lumia phones but there are phones with numbers over 1000.

Also, 950 and 950xl have the same number, the xl showing difference in size, but they also have different SoC (Snapdragon 808 vs 810).

So anyone knows that logic?

from Windows Central Forums http://ift.tt/2rx1eYN
via IFTTT