deleting files for my storage limit

Hello.

I have a storage limit of 1500 GB. I find I have to frequently trim down my usage by deleting files.

I just trimmed down to 1095 GB. But on Seedbucket, it says I am using 565 GB. Why the discrepancy? How can I find the files that are not being provided to the torrent system and get rid of them so I have more space to work with?

thanks!
.pat