Normal gunner mode is like maning an ack or being a bomber gunner. You control the gun completely.
Ship gunnery mode tracks a compass bearing and range, you can move the gun, but it moves slowly to make fine corrections. Intended for use against ships.
Land gunnery mode tracks a specific point as the ship moves. Like Sea Mode, the gun will let you make corrections.
As for the numbers, that's easy:
165 (target bearing) 190 (gun's current bearing)
4.6k (target range) 5.3k (current range setting)
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Flakbait [Delta6]
Delta Six's Flight SchoolPut the P-61B in Aces High"For yay did the sky darken, and split open and spew forth fire, and
through the smoke rode the Four Wurgers of the Apocalypse.
And on their canopies was tattooed the number of the Beast, and the
number was 190." Jedi, Verse Five, Capter Two, The Book of Dweeb 