The computer on your desk has a number of errors just holding values in memory.

Yes, it's not 1%, but the argument is about them being imperfect devices. It's not a horrible thing to start with the presumption that calculators are not perfect.

Yes but I don’t depend on the output of my comp’s memory in such explicit terms and it doesn’t have lasting consequences. If my calculator literally gives me the wrong answer 1% of the time that’s a bigger problem.