Like how does he know what 3 and 7 have on them? And would this work on a windowing system? And why does it appear as if the screen has turned off?
If you boot into the GUI and spend all your time there, then although 1 will probably contain remnants of the boot process, 2-6 will be unused, a blank screen with some text in the corner.
Basically, he's switching between a near-blank screen, and the graphical environment.
So basically it's :
switch to text terminal
wait 15 seconds
switch to X Window