Having trouble with the air gun calculator.

I'm shooting a 10.5gr pellet out of my Gamo Tac at about 680 fps or so. My scope height is 2.25" and 4 clicks per MOA. But the calculator keeps adjusting for clicks up and I just want to know the drops (and above line of sight) are out to 50 yards with a 20 yard zero. It won't let me put a zero in the clicks per MOA, how do I find just the drop? Thanks.