What is the monthly paying day? (1., 15th or day of subscription?)

I have a question regarding the monthly paying option for Storyboard Pro. Is the paying day on 1. or 15. day in the month?
Or is it the day I’ll start the subscription?
Thank you!

I think it’s based on the date that you purchase the license. If you purchased on the 21st, I believe it will renew on the 21st of the following month/year (depends on which license you actually bought). That’s how I read the expiration in my license info page anyway.