If you sight your rifle at 25 yards for a 50 yard zero with a 5.56 55gr cartridge, your point of impact should be roughly 1.3 inches low at 25 yards, right on target at 50 yards, and approximately 2.6 inches high at 100 yards.

This is because the 50 yard zero creates a parabolic trajectory, which means that the bullet will rise above the line of sight as it travels to its maximum point before falling back down and crossing the line of sight again. By sighting in at 25 yards, you are effectively shortening the distance at which the bullet is traveling along this trajectory, which will cause the bullet to impact lower than the line of sight.

However, this is just a rough estimation and your specific firearm and ammunition may result in slightly different impact points. It is important to verify your zero and make any necessary adjustments before using your rifle in a shooting situation.