"All circuits are busy now" message instead of "Extension does not exist" when I call a non-existent extension

[nzoli]

Hi all
I’m using FreePBX 15.0.37.1 / Asterisk Version: 16.30.0

I got “All circuits are busy now” message instead of “Extension does not exist” like message when I call a non-existent extension.
How can I change it?
thanks

[Stewart1 (Stewart)]

Don’t use an Outbound Route that matches a short number.

[nzoli]

Sorry I’m new in freePBX, I don’t understand… Can you give a more detailed answer?
Short number mean extension?
thanks