How do you name updates?

I was wondering how people get the numbers for version updates on games, firwmwares etc.
Why does sony's firmwares go from 2.0 to 2.6 for example or why does it just go from 2.7 to 2.71 for example

well why i see it is like the number of new features like 2.81 to 2.82 theres only one new feature i thik thats how sony does it also not sure

-hope that answers ur question