How does bullet drop and MOA work in this game?

Been trying out sniping at Hotel. Ranged the target on the map and it gave me 300 meters, so I set my zero to 300. Looked like there was significant bullet drop as I was hitting below their feet. The game says ballistics are fairly realistic but it seems way off. Is the zero mechanic broken or am I just missing an understanding of how it works properly?

Is there a way to calculate the bullet speed and type of scope? Are they all MOA or MRAD?