why are you trying to setup a virtual server? what services will it provide?
the inbound port number will be the listening port on the router. when someone from the outside tries to connect to the server, what port will they try to connect to?
the private port number is the listening port configured on the server. The router can change to a different port number than the one the person is connecting to.
most likely these will be the same
80 for http web server