Thanks for the info Glidor!
I wonder if this is worthy of being addressed in a future patch. While some missions are pretty straightforward, others don't make the objectives that clear. A little bit of feedback from COMSUBPAC wouldn't hurt...
Perhaps in the way of more detailed briefings, including maybe the area of patrols and the minimum expected duration or tonnage.
Then again, I don't think all missions should realistically be a success, so failure is always an option.