The letter never goes down with the same build number. The letter stands for the number of compiles for one specific build starting with a. When the same build is compiled again, the letter is b.Beta 2 - 22F5053f
Beta 3 - 22F5053j
Interesting to see the letter go to a higher letter and not the same or down. Beta 4 and 5 see you soon?
So build 22F5053f (beta 2) has been recompiled four times coming out as 22F5053j.
Pretty easy.