Doesn't it seem like a reasonable answer in this age could be to do away with the time function of a microwave altogether?
Do people really want a clock on every kitchen appliance in 2024? I usually will just turn off the clock where possible now and just use my phone for time. Having no clock isn't a problem but having a clock showing the wrong time is a problem.
As someone who doesn't wear a watch and doesn't use my phone while cooking, I find the clocks invaluable. The oven clock usefully shows the time when the microwave clock is counting down.
An alternative could be to let the user do the math, and change it to "Please start cooking in 3h27min for 12min at 600W".