well, for description just put half life
inbound port, 27015, connection type UDP, just adding 27015 should be fine, its what i did, but if u want to add all of the half life ports these are them
Half Life Server
IN UDP 27015
IN UDP 6003
IN UDP 7002
IN UDP 27010
IN UDP 27015
IN UDP 27025
6003-27025 is too big a gap so u will have to add them all seperatly but remember just adding 27015 worked for me.
for private ip address just put the ip address of ur machine u play hl on.
i dont know what it wants for private port