When to count period

Do you count the first day of your period when it’s a flow or spotting?

Some months I start our heavy, some I start out lighter.

Last month I spotted for a day. Then nothing for two days. Then finally after three days I got my period. So would I count the day I spotted or no?

I’m also ALWAYS regular and like clock work. When I spotted 3 days prior i thought it was implantation but I ended up getting a period but it was shorter than usual.

This happen to anyone??