All ships transporting goods to any destination are treated the same, irrespective of flag they carry and the ship-owner nationality, and so on. For instance all ships delivering goods to Hamburg are treated the same and are subject to the levy. All ships delivering goods to Shanghai are treated the same (and currently would not be subject to the levy).
The level of the levy would be announced one year in advance, thus providing cost predictability and enough time for the shipping industry to incorporate the levy in their prices.