What is the reference point for edges angle display? When I display angles for edges these are always 90°, I am wondering what is the reference calculation object of a single edge angle display and how to change it?

PS: I know I can see the angles when selecting a face, however what is the meaning to have these 90° displayed then and can I change it?
(Face Info: angle) gives you the internal 2D angle between two edges, in the plane defined by the 2 edges.

(Edge info: angle) gives you the internal  2D angle  between the face normals of the faces adjacent to the edge, in the plane that would be defined by the 2 face normals, if their origins were brought together.