The Cisco ASA 5510 has 4 ethernet ports, a console port, AUX port, and a management port.
With the Security Plus for the ASA 5510 you can use 2 ports for 10/100/100 and 3 ports for 10/100 (or 5 ports for 10/100).
Where is this fifth port coming from exactly?
What 2 ports are GE?
Sorry I missed your other quesiton. In older code versions, the management port is the 5th port when you use the 'no management-only' command. In newer versions, this just becomes the 5th interface by default.