That page is for configuring port range forwarding. If you are forwarding a single port the start and end port should be the same. The Local IP Adr is the IP address of your minecraft server (should be static LAN IP). Tick the enable checkbox.
Type your local ip address (the IP address of your server). You should configure your minecraft server a static ip. Your friends will connect to your external ip then they will be forwarded to your local ip (minecraft server).
has to be a local address on the LAN. the 127.0.0.1 is NEVER accessible outside any system as it does not 'route'.
the user will need your external IP