That's a nice safety feature for a very dangerous device, BTW: a light that says "off" when lit.
Makes perfect sense. This machine should never be on by accident. You can see from a safe distance if the big light is not glowing, and then something is wrong: either the machine is accidentally on, or then the light has burned out. That's much safer than having a light that says "on" when lit, because a burned-out light might then hide the fact that the machine is active and dangerous!