According to the German Packaging Act, merchants need to register on LUCID (German Packaging Act Registration Office) and declare the packaging quantity. The specific steps for declaring the quantity are as follows:

Log in to the LUCID website and enter the "My Space" page.

Select the "Declaration" tab and click "Continue".

Select "Basic Data" in the "Declaration Type" drop-down menu.

Enter the type and quantity of packaging materials to be declared.

Click the "Submit" button to complete the declaration.

It should be noted that merchants need to declare separately according to different types of packaging materials, and ensure that the declared quantity is accurate. If you have any questions or need help, you can contact LUCID customer service for support.