Often the U-Boat commanders were given a probable number of U-Boats that would show up, and then when they were in contact with the convoy, make call signs to see how many had arrived.
Seringkali komandan-komandan U-boat diberitahu perkiraan jumlah U-boat yang akan muncul, dan ketika mereka sudah bertemu dengan konvoi musuh, membuat kode-kode panggilan masing-masing untuk menghitung berapa banyak yang datang.