It is indeed for the Crush Grind mechism. It's quite annoying that they chose to use such odd sizes, 15/16", 1-1/16, 1-9/16, 1-3/4, surely they could have just used common sizes 3/4", 1", 1-1/2", 1-3/4". As you say, the 1-1/16" isn't critical.
I'll be using metric bits anyway, so mine won't be...