Deleting Time Machine backups doesn't clear up space

[maclook]

I have a 120gb hard drive in my Macbook which usually has about 90gb worth of stuff on it. I checked the sparsebundle on my backup hard drive and it says it is 330gb so I deleted 5 out of 9 backups (one with 5gb worth of movies) and the sparsebundle still shows that it is 330gb. I know those 5 backups are deleted because they don't show up in Time Machine or in Finder. Does anyone know what the deal is? I'm considering just deleting the entire sparsebundle file and starting a new backup, but that kind of scares me a little and don't want to resort to that.