no one knows how much was stolen. It's quite difficult to noticed 10BTC missing out of hundreds of thousands. You could easily write that off as a mistake. That could be extra transaction fees that accumulated.
How is that difficult? This can be done automatically on a continuous basis.
NO discrepancy should be tolerated. Not a single satoshi. There cannot be any "mistakes" if the code is flawless. Anything different, even 1 satoshi is a
huge red flag and reason to persist to work on it until you find and fix the bug before it grows above your head.