It doesnt need to be centered. It needs to be able to be read as the engine is rotated and the plunger of the dial indicator has to ride on the machined ID surface of the pump bore on an auto, or the input bearing retainer bore on a bellhousing. As the flywheel or flexplate or crank hub rotate, the relationship between the spot on the surface it's stuck to and the sides of the bore will not change unless the bore is not centered on the rotational centerline.