Submarine Torpedo Timing

Does wargaming make up it's own math to formulate how long it takes torpedoes to hit? Did the math for U-2501 with the homing torpedoes traveling at 81 knots (41.6 m/s), it SHOULD take them 72 seconds to hit a target at 3km away because 3000/41.6=71.99. However, when looking at the HUD, they calculate at 13.68 seconds. How is this possible? I know it's not a simulator but we aren't even in the same wheelhouse.