If you have changed the availability manually and now it does not correspond to the real state in the calendar, you can do the auto set availability command.

If you have availability that is higher then the real one, you will get the info message above the calendar Availability is set to greater than room type maximum capacity

When you click on that message you will see which room types and periods are with higher availability

When you find that your availability is not good, whether it is less or more than the real one, you can do the auto set availability command located under General settings.

By clicking on it you will get the message informing you that this action will automatically set availability of each room type to the actual number of available rooms for the next year.

Note: All manual changes done will be overwritten. Also, note that this action cannot be undone.