The difference lies in the kind of target that you go after, I suppose
regardless of the 100% realism etc, I tend to aim specifically at the biggest ships whenever I encounter a convoy. On top of that, I tend to leave those smaller coastal freighters alone when I come across them, to save torpedoes for the bigger ships.
That yields scores which are 20k above average since the real Kaleuns would just sink most of what they could get their hands on, including all those small steamers
Oh, and they did not have a screen which said the exact tonnage, they often had to guess.
just another two cents
