If you mean for when you get a bike, chances are you will use about half the life of the rear tyre in a day on the track. So if the rear is low, it will be shot by the end, but a new tyre would easily do another. Fronts don't take as much abuse, probably use about a quarter to a third of the life. This is of course assuming a sticky road tyre, not a sports touring one like I would normally use on the road. E.g. my SV tyres will last about 8k rear and 12k front so I would get more track days out of them than a sticky road tyre which lasts 4k on the rear and 6k front. Either way, you definitely won't use as many as helpimcrap during a RACE, as they would be slick tyres designed to only last for a couple of hundred miles.