Tranch,
Most screw-on recoil pads are about 1-1.25 inch in depth. To prevent making the stock too long, the general practice is to cut off a small amount of the stock so that the total finished length with pad is just right for you. You therefore need to determine if the present stock is just right, too long, or too short and provide this information to the person installing the pad. First, the stock must be sawed off cleanly and perfectly straight or the pad will not fit right. Then the pads are oversize and must be sanded to fit the dimensions and contours of the stock. NOT EASY to do without messing up the stock unless you have experience in such matters.
Good shooting and be safe.
LB