2 Answers
Normal usage for port 80 is an http web server to serve up HTML pages (there are many other file types but for the layman a basic web page).
Port 8080 is the defacto port for listening for proxy servers. The proxy listens on port 8080 and then acts as an intermediary between the client and the web server.
So I think we need to 80 or 8080 depends on the server type (web vs proxy).
You can add multiple rules for the same port. It is allowed