I learned the hard way that you can do a long list of specific availability slots. I lost 9 appt slots I set up because Tidycal wouldn't save it at all. I only found, after all the work, that Tidycal wouldn't save after +|- 5 appt slots.
It would be important to have an alert that pops up after launching the 5th slot saying to save after 5 appointments set up. Or a BIG banner message at the top saying the same.