I’ve never fully understood how the ‘popcorn’ button on microwaves work (I’ve read different things that may or may not all be true depending on make/model), but my current one always runs for exactly 3 seconds too long and ever so slightly burns the popcorn.
It’s not burned enough to throw it out, but it does give a noticeable “burnt popcorn” smell that kind of ruins my day.
So instead of pressing “popcorn” and doing something else, I have to stand there and watch it to hit ‘cancel’ in time.
That’s just how microwave popcorn is. I just put the microwave on for 9 min or whatever large number is easy to start and wait until the popping slows to a second or two between pops. There’s no way to have a perfect amount of time for all brands and packages of popcorn. Not to mention shrink-flation has made the time need to be shorter and different altitude changes how long it takes among other things. I have heard that some microwaves actually have been made with a microphone to listen for the time between pops, but I’ve never used one. But since they can’t be adjusted for your preferences, I’ve heard they usually burn it anyway. It’s always better to have it a little under popped than a little burnt IMHO. Once you do it a few times for a particular brand you’ll find the right amount of time if you need to walk away.