What do you count as the actual start of your period?

B

So I’ve been trying to track my ovulation but I’ve always wondered what counts as the actual start of my period. Every month I start spotting very lightly and it’s usually dark brown which lasts for a few days-sometimes stopping in between- before I get cramps and heavy red blood. So my question is do I count the start of my period on the first day I begin spotting or when I get my full fledge heavy red blood??