Very slightly on topic... Do the Microwave/ready to heat meals there now tell you to measure doneness with a food thermometer? I've been noticing that on ours, and I get a big laugh out of it. Not because it's silly, but because for how many years, people have been eating ready to heat meals without those temperatures granting us permission to eat! (of course, it means they can't be sued if you get sick, so maybe that's why they're all getting on the bandwagon!
And, yes, you could just add 5 minutes to the timer, but maybe the food cooks/defrosts while the oven is heating up to the preheat temp? This could allow dangerous bacteria to form and kill us!!!
or something like that
