You need to do more shooting . Now that you can hit the paper at 25 yds shoot at 50 and re-align the scope/sights. Next go to 75 and repeat. Finally go the the maximum range you will shoot at and see where you are hitting, then adjust accordingly. Not finished yet once you have it sighted in at your max range take a few shots at 25, 50 etc to see where your slugs are going. That is the only way to be confident with your gun.