So I was looking at some stems. I am looking for a 10 degree rise. Now as I understand it's measured from a "line" that is perpendicular to the head tube. When I was looking around catalogs and online some were labeled as 80 degree. Basically this this is the same idea only measuring the other way, from line that is parallel to head tube. So 80 degree stem = 10 degree rise? Yes I know this is a stupid question. Just making sure I am not missing some hidden cycling truth or something.

You got it. It's one of the things that bicycle manufacturers do to try to confuse us.

And some will even refer to a stem as 125 degrees. Meaning, it's actually 35 degrees from the perpendicular.