The values entered into the 'Booked Outside of Block' fields on the inventory page do not impact your inventory and are for reporting and recording keeping purposes only.

Because of this, you have greater freedom with how you use these fields. Their original intent was so that MCP's could gather the data from the hotels on reservations that were created outside of the system and were booked directly with the hotel or using a third party booking platform. 

Please see this video for further details on how you can ustilise the 'Booked Outside of Block' fields: