http://www.subsim.com/radioroom/showthread.php?t=216294
The correct vessels as far as the game is played does not make sense.
The orders you receive are to sink ships entering or leaving Danzig Bay.
That should be any ship when sunk should register on the tonnage bar.
I have precisely concentrated on doing this but makes no difference.
I used to sink ships at rest in the two ports and they always counted, now they do not.
When pressing the black icon this shows the patrol area.
In theory anything within that area sunk should count.