Obviously, the seemingly helpful instructions printed on many microwaves is never actually consulted when using the appliance. The way it's written, it seems to be intentionally adding complexity to rather unambitious goals, like heating up some leftover pizza. This, of course, is to sell microwaves. In practice, people ballpark it, check to see if their food is sufficiently warm, and repeat if necessary. Some microwaves, marketed toward cafeteria managers, are the very model of simplicity. One dial for setting the time. That's it. It turns on when you turn the dial. The world would be a better place with more interactions like that.