This may not be as helpful as you were hoping, but it really depends. I've not built this, but there are ways you can adjust the angles to get what you need/want. Especially the inner bevels to make various angles, if it's off you can make plenty of adjustments. If you're really concerned about getting the angle "just right" and you have Armorsmith, on the pattern layout you can select "Show Edge Angles" to true and get an estimate of the angle between two edges.
Personally, as a "newbie" I wouldn't worry too much about it and do what works for you. You're learning, and a lot of that will come from trial and error.