FCPX Project still huge after deleting generated files

Hi,

My fcpx project is still enormous after deleted all render and optimized media files. I have gone through the project on the hard drive and all that remains is project files that are very very small and original media which is around 100gb. The project folder is still saying it is holding nearly 500GB but i have no idea what it is either hiding or if i am not deleted something properly??

The library properties in fcpx says that the cache is 380GB but i have deleted the render files and optimised media files about 10 times now and it is not making a dent!

Any help or advice would be most welcome.

Thanks in advance