I would suggest illiteracy, yet they were able to write the note. One ad for appliances, a trip through an appliance section in a store…heck, it’s probably spelled out on the actual microwave itself and would show someone how it’s spelled.

I’d suggest it’s deliberately misspelled for effect, but the number of people who keep wrecking basic words like “could of”, too/to, there/their/they’re despite there being plenty of correct examples to read in daily life is far too high for me to assume someone wouldn’t be ignorant, willfully or otherwise.