I was having a hard time interpreting the charts, because of the Vector 22 default skin with Preferences > Appearance > Skin preferences > Enable limited width mode toggled 'on' (also default). I'm on a desktop PC using Waterfox, but Chrome yields the same result as an anonymous user.
The version numbering is right aligned, and the blue bars look blank if this setting is not toggled 'off'.
Probably the simplest fix would be to modify Template:Compatibility PHP and Template:Compatibility DB (or possibly Template:Version history) to conform to the limited threshold.