Well-trained gunnery officers could make calculations themselves and challenge incorrect results from a table. A computer operator likewise needs an independent idea of what the answer should be. Knowing the underlying method allows a check that the output is in the right range. A calculating aid is harder to trust when nobody can recognize a bad result.
Notable Point · 1:24:16-1:24:52
Why gunnery officers needed to check the tables
Officers needed enough practical knowledge to recognize when a fire-control table or computer was giving an implausible result.