The answer's actually earlier in this thread:And what's the golden badge with a number between 2 stars that some memebers have under the portrait and the rank? What does the number mean?
Anyway that bar shows how many games you own. Years ago people like SAS, Veld, and @gigau decided to challenge the forums themselves by acquiring so many icons that the icons alone took up a large part of the page. So a limit was set so that you only could show 50 icons at most and when you reached 50 you got the bar. That was also when it was introduced that you decided which games to show. Previously you showed everything registered whether you liked it or not.
The limit has since been raised to 54, since in the new forum there are 6 icons a row instead of 5 meaining that having it at 50 didn't fill out the last row. So now you get it once you get to 54 icons.
Maybe @AgisTournas could add an explanatory section for this into his initial post?
EDIT: Obviously I just missed @Wagonlitz replying when I hit the thread!