Where does this subdomain prefix come from, and how do I change it?

[BookMark]

Hi,

I am new to Apigee, and still lack understanding. I need to add a new identity zone (under apigee.com/sso), but the prefix (obscured in red) is wrong, and I need to change it. 

Where is this defined?
Where does this prefix come from?
How do I change it?

The prefix here (obscured) is specific to our company, but it got set to the wrong thing, somehow.

Thanks, Brock