I would be very surprised if this isn't just referring to the live DVD. With the number of gigs on this tour, 7 million will be roughly the number of attendees by the end of it. And since xylobrytes definitely sound like something that glows, I'm making the call now that they're the wristbands. Fits quite well if you imagine the cameras looking out at the crowd during Charlie Brown and there are (between all the concerts) 7 million of these xylobrytes 'glowing in the dark' along to the music. And naturally we'll be seeing a lot more of them.