How many different roles does the grading system use?

I know that when you get your grade, it's supposed to account for where you played, so mages played as support are only compared to other times they were played support, and not mid.

What I want to know if the system is only distinguishing Support vs Lane-use (and Jungle I would very much assume), or it it also able to separate which lane you were in. So does [champion] top get looked at the same as and compared to [same champion] mid/bot, or would those games be considered separate for grading purposes.

I'm hoping the lanes are handled separately.