Does it count the first day you get a positive or the darkest the line is?

Marilu. • 36 years old. 👶🏻👶🏻👶🏻👼🏻👼🏻 🌈👶🏻 and expecting...,, YES ANOTHER BOY!!! Team blue forever EDD 11/6/18

A day apart. Got my forts positive yesterday. But today I see a darker line. 🧐