@KingAnon - like Pentakis says, they already know. So you’re not drawing attention to the mistake, you’re drawing attention to your ability to realise your mistakes - and /that/ is a great attribute.
Go find Feynman’s description of how his team fixed the calculations for the Manhattan Project, and you’ll see why it’s never too late to realise you made a mistake, and it’s always worth trying to fix it.
Oh, and when you write to JHU, quote the appropriate part of Feynman’s story, and tell them that you’re borrowing his solution to the problem 