How to zero a scope on an Airsoft sniper rifle?

I recently purchased an L96 AWP Airsoft Sniper Rifle from AirSplat.com. According to Airsplat, the range is 200-250 ft. However, I can't seem to make shots from over 70 feet accurately. I think this is because my scope has not been zero-ed yet. My scope has Elevation(on top) and Windage(on the right). On the knobs, it says " 1/4 inch at 100 yd" meaning that for every click I shift it either counter-clockwise or clockwise, at 100 yd range it will adjust 1/4 of an inch. This is a problem though because according to AirSplat, the maximum range of the rifle is 250 ft, the equivalent of 83 yards. So how do I zero my scope that is meant for 100 yards, when my rifle is only meant to shoot 83.3 yards?