Can't figure mark upfor versions usually it is v<release>.<Major patch>.<minor patch>
I guess fourth one is quick fix instead of using letter? Major patch is like content patch.
Viewing post in AfterShift 0.6.2.1 Patch Notes comments
Release, major, minor, patch.
A major patch will usually be combined new TF, new area, and gameplay, every few months. A minor patch is something tiny like the lock minigame or the restart function, and the rest are just bugfixes or simple QoL.
Technically, the in-game version also is followed by a date, but I don't extend that to the public. Likewise, there should be an extra number added afterwards in case there is more than one patch a day, but I just skip this altogether and upload without a mention, as these are tiny omissions lie not turning off dev helper functions.