You need to get the list of ssid's you want to delete from the volume and then use the nsrmm command.
If it is a Windows box you can put them in a text file remove.txt, one on each line, than create a batch file to remove them with a line similar to the following;
for /F %%i in (remove.txt) do c:\"program files"\legato\nsr\bin\nsrmm -d -S %%i
{note: All on one line!}
Then run nsrim -X -V {volume name} to recover the space.