They are right that if you pull the rear sight all the way to the rear onto that "step" it raises it to the combat setting. That will make it shoot a bit high at 100 yards, but it is supposed to get you hits on people out to 300 meters, not bullseyes. You set the sight down onto the lowest setting lined up with the 100 m mark, then you can go to a 100 yards range(close enough to 100m.) and adjust the front post up or down to make it hit on target, then it is supposed to be calibrated at all the ranges, with that ammo. But I would not worry much about it over 200-300yds, it is not a precise weapon. Unless you are a really good shot and the gun/ammo combo is an exceptional specimen.