Board Thread:Naruto Discussions/@comment-10452902-20170520191921/@comment-734582-20170526064245

Boredfan1 wrote: With the ranking system, we don't exactly know what makes something for example + instead of - or just the normal rank, it is never explained. You're missing the point.

The ranking system exists in-universe to give students and ninja some idea of difficulty. It's not a super-strict categorization. When a ninja says his technique is A-rank, that gives a certain idea of the scope and complexity of learning this ninjutsu. + and - are to give a bit more resolution to this scale IE "this technique is A- whereas the other technique is more of an A+".

It isn't meant to perfectly describe everything, since ninja learn differently anyways and what may be A-rank to someone can be C-rank to another.