HELP, seats are missing!!!!

Hello We bought an old Bürstner WOMO yesterday. This WOMO has 4 sleeping places! But are registered in the registration certificate as I have just seen only 2 seats. But we are 2 adults and two children ( 6 and 8 years). However, on the bench at the table there are 2 pelvic belts. The seller said that these belts would be OK, otherwise the TÜV would not accept them. When I read the approval certificate at breakfast now I almost fell there under S1 (seats including driver’s seat) is the number 2. Unfortunately, the seller can only be reached again from the 05.01.. Or is such a kind of inventory protection??? The WOMO is built in 1991 Please urgently for help, since we want to start the day after tomorrow!! In advance Thanks Paulchen