Allow Me to Explain Incorrectly
This has to be one of the most ridiculous stories we’ve ever read. This guy spends too much time explaining an Excel spreadsheet to the OP, which she created. But that’s not even the worst thing. He even knew that she made the spreadsheet, but he still decided to explain how it worked anyway.
But just you wait, it gets even better. The OP found several mistakes during the course of his mansplanation. This is like the grand slam of mansplaining. She really should’ve cut him off within the first minute to remind him that he’s a total doofus.