Negative torque problem

 void FixedUpdate()
 {
     rb.AddRelativeForce(-10 * Input.GetAxis("Vertical"), 0, 0);
     float turn = Input.GetAxis("Horizontal");

     if (turn < 0)
     {
         turn = -1;
     }
     else if (turn > 0)
     {
         turn = 1;
     }

     rb.AddRelativeTorque(Vector3.up * 10  * turn);//****in this line 10 must be 7
 }

I have this script in a cube and seems work well but too fast for me and decided reducing 10 to 7 in AddRelativeTorque function. But then cube only rotates right (when vector positive) does not rotate left.

Honestly this is just experimental not important but really want to why cube acts weird?