How accurate is the algorithm that Glow uses when it comes to fertile window ?

I used the ovulation tests and the glow app just to see if they would match ... When glow was showing my first fertile day the ovulation stick showed 2 solid lines pretty much the same colour and everything ... Today it s supposed to be my peak day the ovulation stick it showing a solid line and a much fainter one :(( which one do I take after ? I missed both days this month anyways but for next month I would like to know ...