GetAxisRaw("Mouse X") not even close to manual mouse movement

I try to create my own mouse movement but I don't understand why Unity's Input manager has completely different results than mine.

Unity's Input Manager

     Vector2 MouseMovement { get { return new Vector2(Input.GetAxisRaw("Mouse X"), Input.GetAxisRaw("Mouse Y")); } }
 

My first attempt

     Vector3 mouseMove;
     Vector3 prevPos;
     void UpdateMouseInp()
     {
         Vector3 mousePosition = Input.mousePosition;
         mouseMove = mousePosition - prevPos;
         prevPos = mousePosition;
     }

My second attempt

     private class Import
     {
         [StructLayout(LayoutKind.Sequential)]
         public struct POINT
         {
             public int X, Y;
 
             public static implicit operator Vector2(POINT point)
             {
                 return new Vector2(point.X, point.Y);
             }
         }
 
         [DllImport("user32.dll")]
         public static extern bool GetCursorPos(out POINT lpPoint);
 
         public static Vector2 GetCursorPosition()
         {
             POINT lpPoint;
             GetCursorPos(out lpPoint);
             return lpPoint;
         }
     }
     Vector3 mouseMove;
     Vector3 prevPos;
     void UpdateMouseInp()
     {
         Vector3 mousePosition = Import.GetCursorPosition();
         mouseMove = mousePosition - prevPos;
         prevPos = mousePosition;
     }

All three methods give completely different result, first and second attempts vary between 1 and 2.5 times the scale of Unity's Input Manager. And my first attempt just misses a lot movement, sometimes even for 10 frames.

Why are my attempts way off Unity's Input Manager mouse movement? And which is more accurate, My second attempt or Unity's Input Manager?