Period question

Question: So, I think my app was wrong and this is something I’ve always been confused about. This last period I had, I started bleeding VERY lightly and the next day it was still just minimal and not every time I wiped. (So basically two days of this) finally on the third day I was heavy bleeding. I put the beginning of my period in my app at the first sight of blood, but should I have waiting until my first heavy day where the cramps were really bad, which typically always happens on day one? Sorry just super confused about when I should actually document day one of my period!