The 130 was the track angle. From what I understand that equals the AoB if the target was on the same course but dead ahead of me. It is a theoretical AoB in a sense. So here, the target would not necessarily be in front of me, it could be abeam or behind me depending on speed and course at the time of launch.
Both the sub and the target is moving so there is no way of telling really if I am behind the target, abeam or ahead of it at the time of launch or impact, judging only by the sketch and the track angle.
Look at page 1-4
https://archive.hnsa.org/doc/attack/index.htm#platei