Ok here goes.... the raised lip on the inside of the disc is wider than the raised lip on the outside. This is what you would expect to find if the pad area were narrower on the inside.
It would appear that the disc has been machined with a raised step that will reach the wear indicator before the rest of the pad has worn out completely.
Perhaps when you get a moment you could check on your Xfire to see if this is the same. It would literally involve running a finger around the back edge of the disc to feel if the raised step is wider than the one visible on the front. This is easily within reach through the spokes. I interested to know if this is a standard feature on these cars.