Question about the value in column "Used Capacity" under "NetBackup Adimistration Console (8.1.1) / Media and Device Management / Devices / Disk Pools" :
Is this value the capacity which is used after deduplication and if how to determine the capacity of the backups after "un-deduplicating" ( rehydration ).
From GUI please navigate to Media and Device Management/Credentials/Storage Servers there on right hand side select the Pure Disk based storage server and double click on it, on the pop-up window select second tab - Properties, scroll down and read the values there ;) I think you should pay attention to Catalog Logical Size....
From CLI execute this command
nbdevconfig -getconfig -stype PureDisk -storage_server storage_server_name -U
I do hope this helps.
Also same information you can pull out of OpsCenter if you have one. Go to Reports/Deduplication Reports and select from various out there