I deleted a group that had 186 pictures posted in comments and they take up about 0.4 gig of space. However, when I deleted the group, my network disk usage did not go down. I found out that all the pictures of the group are still on the web server.
I bought this problem to Ning's attention and their response:
"Since Disk Usage looks directly into storage, and these files were not deleted from it, they are not deleted from Disk Usage either. That why deleting the group doesn`t affect the storage holdings. In order to clear space on the network, you should to independently delete all unnecessary files."
I told them that was ludicrous. How can I find files in a list of 1000s when I have no way to search the "Files List".
" ... it is a feature of the platform. Unfortunately, it cannot be changed on our end."
Per Ning's suggestion, I painstakingly went through the "Files List", one-by-one, to find a picture file that was pre-maturely posted in a comment. I deleted the comment but the picture file was still on the web server. I finally found the file in the "Files List". It took forever for I have no way of searching within the "Files List". I deleted the file in the "Files List" and it is no longer listed in the "Files List", but is still on the server and can be viewed. It is also considered in my "Data Usage".