Maybe it was simple case of integer underflow... You put negative number and it wraps to positive number due to some systems silently ignoring sign bit instead of returning an error... I was once asked in our own system why one exchange got really big number returned when they tried to send an transaction... I had to calculate the binary version of the number on paper because the number was too big for my computer to understand... when I finally got the number converted to binary, it was really long stream of 1's... essentially part of the code returned -1 but it couldn't show it as that part of the system wasn't designed to print negative numbers.