Custom Service with same start and end port

When I attempt to create a custom service where the start and end ports are the same, the embedded website reports and error "Start port can't be equal to end port"  The software is at least consistent; if I create a custom service with different start and end ports, then try to edit that service to make the start and end ports the same, the same error is displayed.  I have upgraded to firmware version 4.3.1-11.

Also where can I see what predefined services there are?

Thanks