You may have noticed if you are using text-based serialization that a property named “m_LocalEulerAnglesHint” has been added to the transform.
What exactly does this do, and what is it for?
Thanks! 
afaik, it represents the quaternion values stored, that you typed in in euler angles.
(also: wrong forum mate 
)
Oops.
By the way if you want to find out how m_LocalEulerAngles is calculated see Quaternion to three hinge joints - Unity Engine - Unity Discussions