When making adjustments for a shot, adjusting the zero is the best way to account for projectile drop over distance. Since the ranges in game are relatively short, I will show the variable zoom crossbow scope as an example.

When you adjust the zoom setting, the spacing between reticle marks changes. For example in the lowest zoom setting the first mark below the center may be at 120 meters. In the max zoom setting, that first mark below the center may be 72 meters. Rifles seem to work the same, but the ranges are much further so it can be much harder to measure very well.

So in this example, I show if you aim at a target 80 meters away, here is how much below the center reticle your bolt will drop at that range. So it gives an idea how much higher you will need to aim to hit the target where you want.