Entering 0.0 creates a mating interval that does not decrease. The red bar that says whether or not you can mate stays full. Entering anything less than that also does the same result. Entering 1.0 gives you a very long wait time to mate again and entering 2.0 will not increase it much at all. Enter 500.00 to 1000.0 for a reduced wait time by 50% and 999999999999999999.0 to be able to INSTANTLY mate after getting an egg or giving birth.