I would suggest that you make a test cut and then set your hairline. Some motors have thrust bearings which sometimes means that the blade moves slightly from rest to full speed and there is also sometimes a little deflection of the blade and bearing under pressure. The actual width of a cut is the best measure to go by. Make sure you true everything up as Paduke suggested before you get to that point.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.