I'm sorry but anyone that sees a multi million or billion dollar bill on an account that does nowhere near that should not be scared. It's obviously a mistake. Stories like this have happened with banks in my country. Check your account and you have billions in there. Guess what happened to those that withdrew money? The judge told them any reasonable person would know this is a bug. Had to give it back. Same thing here, any reasonable person doesn't get scared.

I’d be concerned as it throws into doubt their entire accounting mechanism