No problem. I had to learn this as GW uses the closed bulkhead idea so you have to hit different spots to sink the ship. Like I said, if you hit the same spot with the GW mod you are wasting you time and torpedos. I also fool around with torpedo speed to hit other spots but that is more of a guessing game.
The check mark updates to the WO. The X clears everything you have put in. The switch in the targeting room also updates your values. You can also open the torpedo doors while at the WO station and also in the conning tower.