I'm thinking if you count the first day of 1 period to another than that'll be your full cycle length
I believe you count the days between the first days of your period. (E.g Feb 6th you start, your cycle runs its course and you start on March 8th,. You count the days in between those two dates and that is your count).
Like I said, I believe. I'm not definitely sure you can probably look up the exact process.
Oh okay! Thank you very much :) I was never really sure about how to do it