ProMods

It goes x.y.z. x being major, y minor and z patch but how does that translate to an ets2 map?

It doesn't matter, your choice. We use 2.x0 for major versions (2.20, 2.30, 2.40) and 2.41, 2.42 etc. for minor versions (bugfixes, compatibility). Also sometimes 2.x5 when it's a compatibility with a new DLC, which required a lot of work to connect all roads (2.25).