There are different types of fullscreen apps. For example, if you maximize IE, it is fullscreen because it covers the entire screen. In this case, you should see the result of 1. Another kind of fullscreen is a game that isn't maximized, but is what is most often considered fullscreen when playing the game... it has no border/etc. In this case, you should see a result of 2. These are the 2 main fullscreen types you'll see and may be the only ones. I think $fullscreen may have been changed a couple of versions back when $tips were added because of tips checking if something was fullscreen or not, so the help file description may be outdated.
If you're checking $fullscreen for some reason, you can pretty much just say if it's > 0, it's fullscreen. Otherwise, it isn't.
