This wierd! After my first patrol my renown points were -2546. So I looked over my patrol logs and indeed my memory was correct all of the ships sunk were legal.
So just to see what would happen I "bought" an officer worth 500 and now I owe 3046 renown points.
The only thing that makes sense is that in 3046 points I can move out of my V11-B boat to a larger one.
Any Ideas on this ??