What is considered the first one of your period?

I’m confused as to when to document the first day of my period is bc it usually goes like this

1. Spotting (red tinted mucus)

2same and ever so often there will be actual blood

3. Usually about the same

4. Usually around this day if not on day 3 then it will be full flow for about 2 days.

Then at the end I’ll spot like day 1 for couple more days then it’ll stop.

So when would y’all say the day I start and end is. Would it be when I start spotting or when it starts steady flowing? I use to count when it started steady flowing but this cycle I did it when I first started seeing bright red blood, but it confuses me bc I’ll be bleeding one min and the next just spottting again. Thanks to anyone who can help!