PS3 eating up too much space!

Hi community. I have a PS3 super slim HEN running on fw 4.87.

The 1TB SSD filled very quickly. Using a file manager, I am getting information from all hdd0 directories and files. The sum is 499 GB!

But the system is showing me only 20 GB free!!

Could this be because I installed and uninstalled many games? Is there a way to retrieve this lost SSD space? Thanks