Each account comes with a dynamic Shuffle row, which expands to allow you do drop multiple bookings in to it, in order to shuffle bookings between rooms. The following video shows you how.
It's important to understand how the shuffle row works.
Let's say you have a booking in a standard double room. If you move that booking to the shuffle row, your availability for that standard double room type does not change. Only when you move from the shuffle to a destination room is availability recalculated - this is to prevent rooms being opened up for sale on OTA's or your website mid-shuffle.
So, in our example, if we were upgrading from a standard double to a superior double, on moving from the shuffle to the destination room a recalculation of availability would take place leaving us with -1 superior doubles than before, and +1 standard doubles.
Bear in mind, that if you have a no show or a cancellation, just parking a booking in the shuffle row will NOT release availablity.