Did you get some sort of error, or are you trying to free up disk space?
If the latter, temporary tablespaces do not drop extents after they've been used for sorts, but hang on to them to save dynamic allocation overhead for later sorts. So the size of the tablespace will reflect the largest sort(s) you've done in there. The tablespace may show as being full, but it has space available for new sorts.
You'd have to drop and recreate the TS to change storage parameters and datafile size.