What is a shared folder quota?

I had this issue on my RackStation NAS the other day; I couldn't write anything to a volume I had created (let's call it newton2). I looked at the RackStation console and unchecked this "Enable shared folder quota" box pictured below.

Enabled, but unable to write to newton2:

Disabled, now I'm able to write to newton2:

Can someone explain what this option means? Why was I unable to write to this volume while this option was enabled?

Solution 1:

There's currently 6.56 TB used on your share. Therefore, it's already over the quota of 1 TB you were setting. If you had chosen e.g. 7 TB, there would have been some quota left. The rest is a dictionary definition.

quota (noun, ​ /ˈkwəʊtə/)

a fixed limit on the amount of something that someone is allowed to have or is expected to do