The patrol point in question seems to be the one with the flag. That one I do not bother staying near to finish the goal as there is no real patrol area. If there is a port nearby I like to sneak in and sink the smucks that are moored there. Otherwise I head for richer waters and look for a convoy or some nice ocean liners
to sink. This flag is not really a patrol but a deploy to mission. Patrols are talked about next.
The other matter is the patrol icon which is a pair for binoculars. I have finished those without even one sighting of another ship (much less a sinking). Since I do not know if it is km or nm for the 100, I tend to remain within a 56nm radius (100km). I usually use the compass and set up a few circles to help me with that. I set a 56nm radius, 50nm radius, and a 45nm radius. I usually keep my run within the 45nm radius unless I see a contact. If I see a contact I will be willing to stalk it to halfway between the 50nm and 56nm radius because of a possible margin of error. Most of the time I just send my reports and get the heck out of dodge (I get my sinkings done on the way there and back with convoys which are radio'd in to me).
Good luck and I agree, if we are "deployed" but run out of torps before we get there we should not have to sink the req tonnage (I am guessing that it is 10k tons).
Well, good luck
~F~