FYI, if your gun is zeroed at 100 yards, the bullet could be high at 140, and thus you would need to aim low.

Picture a line that is straight as a laser - this is your line of vision through your scope. Then picture an arc, like the path of a football through the air, crossing the straight line twice - this is the flight of your bullet. Accordingly, if your scope is sighted in at 100 yards, your bullet will be high at 110 and 120 yards, etc. The bullet then starts dropping at some point, lets assume it is approximately 140 yards. The bullet will drop until it is zeroed again at about 180 yards. Past 180 yards you would need to aim high.