Logging your period

Katie

I'm looking for some good advice about logging my period on Glow. I'm not really sure what I should consider the start of my period. Sometimes I'll have very light spotting and periods of no spotting a few days before I really need to use a pad. Should I be counting the spotting as the start of my period even though it's not much? What do other users do? I want to be accurate because I use the calendar to track when I'm most/ least fertile.