Decision. The published fuel level on the boat can only fall. It rises for exactly one reason: I declare a refill through an explicit door built for that purpose, and only then is a rise believed.
Because. Diesel is a physical invariant — it never goes up on its own, so any observed rise is a measurement artefact, not fuel. The camera-based tank reader guessed at refills by watching for both tanks rising together; correlated lighting artefacts raise both together too, and the published level swung around while the boat sat moored. The heuristic was removed because it inferred — and inference was exactly what made the number untrustworthy.
Instead of. Smarter inference. The interesting problem was not the rule but the trap it creates: miss a refill and the number is stuck wrong forever, looking confident. So the reading can pin — when the raw measurement sits persistently above the held value, the display shows both, says pinned, and asks whether this is a refuel. A stuck number is never silently stuck; it announces itself and offers the door.