Why is this so unbelievable? As in, is the number too high or too low? Because out of two relationships I've been in my life, both of them used apps to track pe

Why is this so unbelievable? As in, is the number too high or too low? Because out of two relationships I've been in my life, both of them used apps to track periods and had near 100% accuracy doing so. Not that it should be used as a replacement for other forms of contraception, rather with, or just as an information.