As far as I know, ipv6 is for the future but I do not think ipv6 ip addresses have even been allocated out to people yet.
I must admit, seems strange instructions for port forwarding. My router only asks for private and public ports and private (LAN) ip address.
I think ignore the Firewall summary page.

Click the Firewall Settings button. Then by the looks, you click the Advanced Settings tab. Then select your computer which should show in the drop down list. Then Click the Add a new user-defined application link.
You will make two entries, one for TCP and another for UDP.
So check option for TCP in first entry, then add a port number. Perhaps 6346 or 6348. This port number must be the same as the port you add in LimeWire's Advanced settings for port forward.
For Profile Name, the Application Name you can type in LimeWire. When you have added the Application Name and the port From and To numbers, then click the Add Definition button.
Do a second definition entry for UDP.

After doing the UDP addition, press the Back button. You will see LimeWire listed in the list of applications, select it and click the Add button which will move it to the Hosted Applications section. Then click Done button at bottom of screen.