Im using the easton flatline 400spine.. how did you come up with the math? so say I put it at 25yards. Then how would I come out?

If I told you I'd have to kill you. Just kidding. There are a number of on line archery ballistics calculators you can use if you know a few numbers.

http://www.outdoorsden.com/archery/archbal.asp
I'm going to assume a 28" arrow. Your total arrow weight should be, with a 100 grain tip, about 345 - 350 grains.

If you use a 25 yard zero then you would be 3.5 inches high at 12 yards, zero at 25 yards and 3.5 inches low at 30 yards.