Deleted share not released space

As I was close to filling the 3 drives I have in my Drobo FS (3x3TB), I have deleted a share. Although the share has disappeared from the list the space on the Drobo is still showing as taken (around 1TB should have been freed) and Dashboard (and the lights on the front) is still telling me I should get another drive.

As the share is now gone I can’t see how I can remove the data from the drive. Can anyone help?

Try to delete trash & restart computer

It’s not in trash. The drobo is on my network, deleting shares on the drobo does not put the data into the computer’s trash.