Hi everyone! Im really confused about this supplement, and i don’t know where to buy it either! My friends and I are travelling from Amsterdam to Frankfurt in August, and we’ve already booked our seats on the DSB website (as it wasn’t still possible on interrail website). There was nothing about any supplement on this website, but if i look this train up on the Interrail app, or on the online planner, it says that a supplement is required. Does anyone know what this supplement is? And where we can buy it? We’re travelling on an ICE on the 28th of August. Thank you very much!!