Random Raycast inside crosshairs

I am trying to get my raycast(bullets) to shoot inside the spread of the crosshairs. The crosshair is made up for 4 GUI.Box's that spread based on a number of things.

Screenshot of what I'm trying to achieve. I would want the raycast to shoot randomly in the green area which is variable based on the crosshairs spreading.

Spread class:

     public class spreading
     {
         public float sSpread = 20;
         public float maxSpread = 40;
         public float minSpread = 2;
         public float spreadPerSecond = 20;
         public float spreadWhileShooting = 50;
         public float decreasePerSecond = 25;
         public float maxForwardSpread = 25;
         public float strafeDecrease = 45;
         public float moveForwardSpreadPerSecond = 45;
     }

Crosshair drawing:

         GUI.Box(new Rect(centerPoint.x - (width / 2), centerPoint.y - (newHeight + spread.sSpread), width, newHeight), GUIContent.none, lineStyle);
         GUI.Box(new Rect(centerPoint.x - (width / 2), (centerPoint.y + spread.sSpread), width, newHeight), GUIContent.none, lineStyle);
         GUI.Box(new Rect((centerPoint.x + spread.sSpread), (centerPoint.y - (width / 2)), newHeight, width), GUIContent.none, lineStyle);
         GUI.Box(new Rect(centerPoint.x - (newHeight + spread.sSpread), (centerPoint.y - (width / 2)), newHeight, width), GUIContent.none, lineStyle);

Example shooting that makes crosshair spread

 if (Input.GetKey(KeyCode.Mouse0))
         {
             spread.sSpread += spread.spreadWhileShooting * Time.deltaTime;
             Fire();
         }