Aug. 15, 1942 - Tambor returns to Brisbane from her 1st patrol. Sunk 1 destroyer, 6 merchants and 4 small craft (2 large Sampans, 1 fishing boat, 1 crab boat).
30,729 tons.
Awarded participation trophy.
I'm guessing because I'm playing at 80% game difficulty (no manual targeting and stabilize view not disabled).
I did take the liberty of modifying my battle flag screenshot (I added four smaller merchant flags for the small craft and a star denoting one patrol).
Yes, this does add an element for immersion.