Port 548 Open But How?

I tried to map public 548 to a local IP 548 port but there was a conflict..

I port scanned my AEBS from the WAN and sure enough it came back that 548 AFP over TCP was open. How can this be : I haven't opened it????

Wasn't the only one as well:

53 Domain
139 netbios-ssn
445 microsoft-ds
554 rtsp

I assume these are needed for some techno reason...

Strangely a port scan doesn't seem to show mapped ports are open... I have a range of Torrent ports mapped and a port scan doesn't show these as being open...??