We have 2 fields that you can use for your own record keeping.  These are purely text fields - there is no calculation done on these fields.  

Originally Contracted - you can use this field to enter the number of rooms originally contracted.

Actualized Pick-up - you can use this field to lock in your actualized pick-up.

As with all fields in the inventory, you can enter a value in the first column and click the arrow to fill all nights with the same information.