Here are two ways to view your Volume usage...
In Windows, if you were to go to NetWork Neighborhood, and double click on the Server object, then right-click on the Volume in question and select Properties. Go to the NetWare Volume Statistics tab and look what it says there. That will give you an entire breakdown of how the Volume is being used.
You can do the same thing through NWADMIN32 by highlighting the Volume Object and selecting details.
Another way to do a complete volume purge is to dismount the Volume and run VREPAIR against it, selecting Purge Deleted Files as an option.
Good Luck!