RN 516 available space?

I have a 516 with four 4TB drives. It’s set up in RAID 5 (one X-RAID volume). Up until a couple of months ago, there were 5 shares.

I recently added a new share and copied over about a 1.2 TB of files (several hundred 1-4GB each) from an external drive connected to a Mac.

I’ve been going through the files on the new share on the ReadyNAS and determining where to put them on the existing 5 shares. After copying the files onto the new share, the file system on the NAS and on my Mac (Finder) showed that there was about 6.8 TB free.

I’ve copied about 600 GB from the new share onto the existing shares and then deleted them from the new share. I also simply deleted about 600 GB from the new share. It seems that I should have somewhat more space than when I started, say about 7.3 TB free, but instead it’s showing 5.75 TB free. It’s as though they were not deleted.

What I can’t figure out is, after deleting almost all of the files on the new share (There are less then 90GB on it.), why has my total available space diminished to 5.75 TB?

Also, when I hover my mouse over the horizontal bar chart on the Shares page of the admin screen it’s showing:

3.59 TB Data

2.08 TB Snapshots

5.23 TB Free

It seems like a lot of space is being used for Snapshots. No? Is there a way to decrease that?

Thank you for any assistance you can provide.