Pending Bookings keep the Rooms Available
The Status of the Bookings is given by the payment option chosen upon confirmation. Active bookings can be either Pending or Confirmed. Bookings with status Cancelled will never keep the rooms as unavailable.
All the Availability Calendars of the front-end and back-end will only consider the bookings Confirmed because those are the only ones that can keep the rooms, or some units of the rooms, as unavailable on certain dates.
If you are using a payment option that applies a Pending status until manual confirmation from the back-end or until a valid payment will be received via credit card, then the system will keep the rooms booked as "locked" for the amount of minutes defined in the Configuration page, in the setting "Waiting Minutes for the Payment". Once a booking gets saved from the front-end, the booked units of the rooms will be locked until those minutes will expire. Once the minutes will expire, the booked units of the rooms will become available again unless a valid payment has been received or an administrator has manually confirmed the booking from the back-end.
Locked records will not be displayed in the availability calendars but from the Dashboard page of the administrator section, it is possible to see which rooms are currently being locked and until what date and time. From the same page, it is also possible to unlock those rooms and make them available for booking again.