Ilford MG Filters, up to 7?

A friend of mine gave me a pack of these today, and I haven't had a chance to try them out yet (Spent the day in Michigan picking up a DeVere 8x10, Durst 4x5 and an cute MP4) but these filters raise a curiosity, do they really go up to "7" or do they only go up to "11", in the sense of the arbitrary number knob.

I thought they only went up to 5, starting at 00, then 0, 1/2, 1, 1 1/2 etc. until 5.

...probably a mismatch due to some conversion between metric system and imperial units...

My enlarger goes to 11. Look, right across the board, eleven, eleven, eleven and... it's six contrastier, isn't it? It's not five.