Unity SphereCast HitInfo Give me an interpolation of the normal surface?

I’m doing a SphereCast for a GroundCheck of a player. I have my Raycast hitInfo, and here in the picture at the left, I Debug.drawRay in black the direction of the hitInfo.normal every frame

It seems like hitInfo.normal give me an interpolation of the normal, not the real normal of the surface…

I only want the real normal of the surface… (red normals I have draw on the right), and may be the green one (the perfect normal between 2 surface), but if I can have only the red one, it would be great

How can I do it ?

Thanks ! enter image description here