What is correct in this situation?

The sign indicates that you are leaving Wilster and are on your way to Schotten, which is 6 kilometers ahead. The red line across "Wilster" signifies the end of that built-up area.

In German traffic rules, this means that you have left a place with specific regulations typical of built-up areas, such as reduced speed limits and additional traffic controls. Once you pass this sign, you need to be aware that the rules for built-up areas no longer apply, and you may need to adjust your driving behavior accordingly.

Understanding such signs is crucial for safe driving, as it helps you anticipate changes in speed limits and road conditions.