Well, if you have fifty thousand, you have 50.000 or as them other people would write 50,000 :-). If you were to type five thousand, you'd write 5.000 (or 5,000).
If an error was made typing, you would read it as 50,000 but it would be typed as 5,0000 (5,000 plus the additional 0).
It would have been better if I typed "Someone quickly read that form and noticed the total of 50,000 (which was actually typed as 5,0000)."
Sorry if it wasn't clear.
Walter