It was late
The figure you quoted was one, then another figure had to be added because of a government media crack down. There was evidently quite a panic, with all kinds of rumors.
The show had nice interviews with some of the U-boat commanders that took part. One fellow said he took great risks to finish off a tanker by going in between the tanker and the city where he was silloueted against the burning ship. The reason was he was fearful that if he missed with his deck gun, a stray shell might have hit a motel or something.
Also good footage of returning heros getting smooched by lovely ladies with flowers.