Leupold customs shop and the VX-3?

Now i am going to buy a leupol vx-3 8.5-25-50mm and I am going to have leupold build the m1 tactical turrets into the scope instead of the target turrets. But I am also going to have them build the bullet drop compensator into it aswell. Now how do they now how much my bullet is going to drop at 500 yards. Becuase all they aske me is the caliber, what type of bullet it is, what the coeficeent is (sorry for the spelling) the altitude and average temp. They never ask me what my ballistics are or anything. And if anyone has had this done could you tell me what you think of it and how accurate it is. thanks