4 inches low at 25 yards = 16 inches low (approximately 16 moa) at 100 yards.

If 1 click = 1/4 inchs (MOA) at 100 yards you will need to go 64 clicks up to get to zero.

I would suggest going half of that (32 clicks) and shoot again at 50 yards, then go from there.

Don't know how you have it mounted, but you may consider going to a gunsmith and putting some sort of shim under the rear mount to raise it slightly.

Good luck