What i can see on the naming scheme, is that the J names seems to be for Russian license build, but that would fit with the J-10 and J-20 :huh:
Or perhaps tenths are reserved for domestic designed aircrafts? (J-10, J-20, J-30... etc)
What i could see was that Migs got a number between 0-10 and Sukhoi's got between 10-20, but then again, the Migs are of older design compared to the Su's...