Big Ed, the additional water on the eggs directly increases the humidity and basically lubricates the chicks shell and the chick making it easier for the chick to turn and finish pipping the shell to get out. It is almost always recommended to up the humidity for the last couple days of incubation. To much or to little humidity during incubation will often result in chicks with disabilities. Often crooked toes or crooked necks, or chicks that never make it out of the egg.