Why did you let them search your car (or why were you driving high/smoking pot in your car)?
What's the worst case scenario? Depends on the state and your age, the volume of marijuana really doesn't matter because the state will crucify you thanks to the scale. You likely will lose the car through forfeiture and may be sent to jail depending on your past history.
Is the scale going to interfere with the case? Nope, it's going to make it.