I searched on YouTube for AutoPath Boundaries Setup. There are a bunch of videos on it, many by John Deere. There was one specifically on Align to Boundaries (that one will likely address your question). Here’s one that explains the basic theory

https://youtu.be/SXs0AAa49Yg?si=f8w0FKM_j5cSjKKp

You can mess around create a plan in Op Center and it will give you an idea on how it works