Assuming you want to run a chalkboard showing the most sucessfull U-Boat commanders you should go for "Erfolgreichste U-Boot Kommandanten".
It was a "Tonnagekrieg" (tonnage war), so it's all about "Versenkte Tonnage" (sunken tonnage).
Simply list the commanders with their monthly/over-all results.
A chalkboard would not list them according to their ranking.
A monthly report for Berlin would do so.