See, it provides a breakdown of how many Achievements and Gamerscore Points you have over how many you could have possibly earned. For example, my Gamerscore is currently 14105 out of a possible 78705, as I've earned 819 of 3607 Achievements across all of the Xbox 360 games I've played. Seeing this just makes me feel ...less than.

There's also a figure for "complete" games in which you've earned all possible Achievements. In my case, one, with the icon for Cloning Clyde looking quite lonely. I wouldn't worry about Clyde though--he's been alone there since 2006. He's used to it.