The OZ (Pos numbers) never have a dot at the end in Excel. In the following image, FALSCH means wrong and RICHTIG means correct.
When you install "GAEB-Online 2021", a pattern file is installed on your computer. You can find this sample file via Start | Program group "GAEB-Online 2021" there in the Import Sample folderor as a link named "GAEB-Online - Link to Import Sample" on your desktop. With this file you can test the import or you can use this file as a template for your Excel data.