Software Testing "Popcorn" button

I made myself some microwave popcorn for a snack just now.  Placed the popcorn bag in the microwave, pressed the 'popcorn' button and then 'start'. Someone next to me said: "There's a popcorn button?" Um, yes, there is.  In fact, there has been a 'popcorn' button on every microwave oven I've ever seen.

I explained to my colleague that the recommended time on the bag (in this case it was 2 min 30 sec) doesn't work on every oven.  Different ovens have different power output and so the actual cook time may vary.  If I go with the default time, it might burn or be under-done and leave too many unpopped kernels in the bag.  You could figure out the correct time in a few ways.