That's how it works. There's a maximum amount ("Höchstmenge") where they close the case when you are below that. The maximum amount varies between federal state

That's how it works. There's a maximum amount ("Höchstmenge") where they close the case when you are below that. The maximum amount varies between federal states, so Bavaria and twelve other states are quite strict with a limit of 6g while four other states have a higher limit of 12g or more.