For reference, it goes like this: (not sure about the actual terms)
Code:
5. 04. 00
Game ver.Major ver.Minor ver
The minor version is usually not reflected in the interface version, except for the very first release, it seems. (first MoP version was 50002 or something iirc)
We haven't had major versions in the tens since vanilla (and probably never will again, I guess), but that made the formula more clear. Version 2.1.0 was 20100, while 1.10.0 was 11000.