How long and fast do teeth travel through the gum?

We are observing a canine coming down through the gum. My dentist said although my dau. is 12 y.o., the canine is just two thirds the way down and "still high up in the gum" on x-ray (not visible by the eye). An orthodontist said teeth travel two thirds of a millimeter a month (about). How many millimeters does the canine have to travel before it reaches the gum line? or what is the total distance canines travel to begin eruption? - thanks for any helpful answers!