MathSignedAngleBetween Method

a and b are the vectors for which you want to calculate an angle, n would be the normal of your plane to determine what you would call "clockwise/counterclockwise" If you imagine the from and to vectors as lines on a piece of paper, both originating from the same point, then the axis vector would point up out of the paper.The measured angle between the two vectors would be positive in a clockwise direction and negative in an anti-clockwise direction.

public static float SignedAngleBetween(
	UnityEngine.Vector3 a,
	UnityEngine.Vector3 b,
	UnityEngine.Vector3 n
)