Well, lets tie this up:
200 mph + 100 mph = ? 300 mph
1 apple + 1 apple = 2 apples
v1 + v1 = nonsense, since you cant add "versions". You just progress to the next version in favour over the old one. You are comparing nutz to peabrains.
I am sure we got an explanation in school for that "unit" problem. But, since I am an old fart and school is quite some time in the past I don't remember what it was.