The elevation knob should have an arrow and a "U" or a "D". This means if you turn the knob in the direction shown as "D" the bullet point of impact will move DOWN. The windage knob should have an arrow showing which direction to turn it to get the slug to move "R" or "L".

Make your changes so that your slug strikes exactly on the point of aim at 25 yards. Then put your target out at 50 yards, and zero the gun again to put your slug about 2" high at that range. You now will be no higher than 2" at 75 yards, and pretty close to dead on at 100 yards.