I’m not a UX expert except in the sense that I have experience using things. Still, I spend a lot of time at work serving as a proxy for users in design discussions. It’s hard to get UX right, even on relatively simple experiences like a microwave oven.

Years ago, my systems analysis professor got on a tangent about user interactions. He pointed out that it can be faster to enter a minute on a microwave as 60 seconds instead of one minute, that 111 seconds is faster to enter than 110. Design choices (including the design of instructions and documentation) that seem obviously correct are sometimes incorrect for non-obvious reasons.

It took a little while, but I eventually discovered that the “Quick Set” menu doesn’t have pre-programmed settings, it just adds a zero to whatever code is entered. So the quick set to cook two slices of bacon (20) simply sets the time to 2:00. In that sense, it functions less as a shortcut and more as a list of cook times.

On a whim today, I tried to warm a cup of coffee by using a quick set code of 6 instead of 10. It didn’t work. Apparently the microwave requires quick set codes to be exactly two digits. For a one-minute cook time, the quick set is hardly any quicker than a manual entry.
My microwave came with the house, so while I don’t know exactly how old it is, I know it’s at least seven years old. Maybe recent microwaves have a more sensible UI. Or maybe it’s a problem that will never quite be solved.