Depends on the site. Some sites have over a hundred. Some very few. This site has >20 at the moment. Opera proxy ports about 10, Avastsvc, another 10 and they're closing as I write this. Some may start with 5 or so, and close all but one. Mostly to remote port 80 (http), some add porrt 443 (https) if you need login.
Far as I know, all of this is totally normal.