What are the options in the "Interface" drop-down?
Name - put in a name
Interface - all is probably ok
Protocol - Select TCP, UDP, or both if an option or if you know what protocol is used by minecraft
public begin - 25565
public end - 25565 This is the port from the Internet coming in to your router
private begin - 25565
private end - 25565 this is the port used by the minecraft server
private IP - the IP address of the minecraft server
remote IP - leave blank