The Classes Per Week setting within a Series/Contract is tied to the Reservable Window and the Reservable Days that the studio is set up to have. If the window starts on a Tuesday and the studio has 9 reservable days, then the week will actually be 9 days and start on Tuesday.

For example, if a customer has a series that allows 7 classes per week, that customer can book their 7th class all the way up to the 9th day of that week. They would have to wait until the schedule opens up the next week to book the next week, though.