I swear I just put $500 in $20 bills in my bank account but then the machine counted the money and said it was only $400. So I was like wtf and I asked the machine to give me my money back and I counted the money and it was $500. So then I put it back in again and it said $400 again. So I took the money back and put it back in but this time in groups of 100 and at the end it only added up to $400

The only two explanations are either that the machine fucked up at some point and took some of my money but there is another explanation and it's that I can't count to 500. Maybe I counted in groups of 4 thinking that 4 times 20 was 100 and counted 5 times that and got to 500 that way. But I don't think I'm that fucking stupid?