Pose Editor Question: Weights above 1.0

I’m trying Mayas Pose Editor starting with an A-pose for neutral. A rotate values are at 0 0 0
I have a twistUp pose at 90deg rotation and twistDown , and various other arm poses at the shoulder: straight forward, straight out to the side, and handing down.

I am trying to test it, so I put an arm pose above his head (rotate the upper arm joint so the elbow is above shoulder level. However, I noticed the twist Up weight reads 1.9 and the twist down is 0.9. The actual rotation values of the arm are -89, -42, -48.
Why do the twist weights read so high?
Why would they both trigger?
why is twistUp beyond 1.0?
Any thoughts?