what exactly is this?

[Gearbox]

http://vgchartz.com/swlaunch.php?reg1=All&game1=Demon's+Souls+-+PS3[31689]&reg2=All&game2=Valkyria+Chronicles+-+PS3[18897]&reg3=All&game3=&weeks=100&weekly=1

k so i usualy go on the charts and compare games, but normally it gives me a LINE graph. Not a bar graph? what exactly is this graph showing me?  


maybe its just a glitch? cause when i put a difernt game in slot one i dont get that random graph