Not sure what you're asking. In both LR2 or 7k scratch skins the keycount is usually denoted as "7k+1". Meaning you have a scratch key AND a middle key. (Unless you play symmetrical style but then it's better off simply being denoted as "8k")
There's no such thing as scratch 6k+1 as of now in any games (though in djmax 7k, since the middle key is dual mapped, it's technically 6k+1. But it's still not a "scratch"). Plus it's the same story with 5k+1 as 7k+1 (middle key AND scratch key)
Unless you're just talking about whether or not to use the spacebar in general 7k, then you can maybe check these out
t/196791 t/171370