Number release

I see the release numbers as abnormal.
A big update i expect second number change 1.Y the Y should be change. A littler update i expect its 1.3.x. here the X should change.
I expected the oktober update was the big one and the small one is the san update.
If there is a hotfix then for example 1.3.1.z where the z is the letter for hotfix/bug update