I am guessing you are referring to the versioning explanation that was posted way back in iOS 10 days? If so here is the copy of that post. Credit to @dreadlord https://forums.macrumors.com/thread...culation-thread.2027218/page-32#post-24378406
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Explanation of iOS build numbers
14 = Major version. Here it says it is an iOS 10 build. '13' means iOS 9 so on so forth.
E = Minor version. First major version starts with 'A' which is x.0 launch release. iOS 10 (14A403). It is not necessary to be a 10.x point release to increment this it may be 10.x.x release. Usually Apple increment this when kernel version changes.
5 = It means that this build is not prepared for public release. Builds have this in build number will not release as stable build.
269 = Actual build number. It means that it is the 269th build of iOS 10.3. There may be a lot of code changes. Generally Apple has a new build everyday. And Apple tests these builds 1 week before releasing it. So, 14E269a went to Apple test team last week to test if there is a major bug. If there is see the next:
a = Revision letter. If Apple test team find bugs, they sends a report to engineering team. Engineering team tries to fix some of them and increments the revision letter. It looks like test team hasn't found any bugs to be fixed before releasing it. So, Apple released to us.
So what can we understand from today's beta?
The build number has '5' before the actual build number. Hence, this is not the build we will see when Apple releases iOS 10.3 stable. I personally expect one more beta, but it may have '5' before the actual build number. Last beta of the iOS 9.3 release is iOS 9.3 beta 7 and its build number is 13E5234a, public release iOS 9.3 build number is 13E234. It means that Apple hasn't prepared beta 7 build as final release but it looked promising, so they released it as it was.
See?
iOS 9.3 beta 7 = 13E5234a
iOS 9.3 final = 13E234
We do not know if final release is same as beta 7. Actual build numbers are same but revision letter may be 'b' instead of 'a'. But very minor thing changes in revisions.
Can revision letter say how good build is?
Well... I think, yes. Take a look at iOS 10.3 betas:
iOS 10.0 beta 1: 14A5261v
Do you see 'v'? Yes, Apple has a, b, c, ... v revision builds before releasing the first beta of iOS 10 to fix some minor bugs before introducing shiny iOS 10 to us.
iOS 10.3 beta 1: 14E5230e
iOS 10.3 beta 2: 14E5239e
iOS 10.3 beta 3: 14E5249d
iOS 10.3 beta 4: 14E5260b
iOS 10.3 beta 5: 14E5269a
It can be clearly seen Apple test team found less and less bugs and reported to engineering team. As result revision letter comes close to 'a' (finally we see 'a') as final release approaches.
One last note, revisions generally happen in 1 or 2 day(s). It is pointless to spend much time in one build, because they have a new one already. I mentioned that Apple sends builds to test team 1 week before. So, when test team sent the report of 14E5269a, engineering team probably was working on 14E5272a. Moreover, iOS 10.3 is not the only branch they are working on. They are working on iOS 10.3, iOS 10.4, iOS 10.4.1 and iOS 11 at the same time. So, it is very complicated actually.
What's next?
I expect one more build as:
iOS 10.3 beta 6: 14E5275a
iOS 10.3 final : 14E275/14E276
How do I know these?
I am a software engineerMost companies use build systems like Apple does, and the logic is same. For example,
Latest Google Chrome release: 56.0.2924.87
56 = Major
0 = Internal version. It has no purpose.
2924 = Minor
87 = Revision
I hope I've explained the build number thing as clear as I could.
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This should be a pinned post. Perhaps we create an “Advanced Beta Speculation” thread for iOS 12 and you have to pass a test on this to be admitted. (j/k Macrumors...we would never do anything to limit anyone's ability to post. )