First off, I'm no DBA just a server sys admin.
I run a maintenance plan on my Prod DBs every week that used to shrink the DBs but after doing some investigation I see that shrinking regularly is a very bad idea so I have removed shrinking from the plan. However I have a 55GB DB that has 10GB space available and the shrink from the maintenance plan (before I removed it) never seemed to free up the space. Backup times and space are a bit of an issue on the server so I'm trying clean up as much as I can. Why would the DB still be showing 10GB free space after a shrink?