The number of grafts depends upon two factors (1) the area that has to be covered which in your case is determined by where you wish the hairline to be placed and (2) the thickness of your hair shafts (hair bulk). The need for a second hair transplant is frequent when the hair bulk is low (fine hair) and less common as the hair shafts increase in thickness (medium or coarse hair) so it is difficult to give you an exact estimate other than to say that the range of grafts may be 1800-2500 grafts give or take a few