Rewriting a bullet count GUI to run more efficiently

ive written this code to create individual bullet icons on the screen space. Each time the weapon is fired via an Input the bullets are removed one at a time. My question is what is a better way to write this code. Im obviously new to scripting and dont quite understand how to smash code down to make it efficient.

 #pragma strict
 
 var shell : Texture;
 var grayShell : Texture;
 var numBullets : int = bulletTotal;
 var bulletTotal : int = 7;
 var screenPosX : int = 565;
 var screenPosY : int = 1040;
 
 
 
 function OnGUI () {
 
     /*
     for (var i = 0; i < numBullets; i++)
         GUI.DrawTexture ( Rect (800, 550 + i * shell.height, shell.width, shell.height) , shell, ScaleMode.ScaleAndCrop, true);
     */
     
     GUI.Box (Rect (869, 500, 200, 100), "ammoCounter");
     
     if (bulletTotal > 0){ //Gray Shells
         GUI.DrawTexture (Rect ( screenPosY, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
         if (bulletTotal > 1){
             GUI.DrawTexture (Rect ( screenPosY -20, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
             if (bulletTotal > 2){
                 GUI.DrawTexture (Rect ( screenPosY -40, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
                 if (bulletTotal > 3){
                     GUI.DrawTexture (Rect ( screenPosY -60, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
                     if (bulletTotal > 4){
                         GUI.DrawTexture (Rect ( screenPosY -80, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
                         if (bulletTotal > 5){
                             GUI.DrawTexture (Rect ( screenPosY -100, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
                             if (bulletTotal > 6){
                                 GUI.DrawTexture (Rect ( screenPosY -120, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
                                 if (bulletTotal > 7){
                                     GUI.DrawTexture (Rect ( screenPosY -140, screenPosX,  grayShell.width, grayShell.height), grayShell, ScaleMode.ScaleToFit, true);
                                 }
                             }
                         }        
                     }
                 }
             }
         }
     }    
     
     if (numBullets > 0){
         GUI.DrawTexture (Rect ( screenPosY, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
         if (numBullets > 1){
             GUI.DrawTexture (Rect ( screenPosY -20, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
             if (numBullets > 2){
                 GUI.DrawTexture (Rect ( screenPosY -40, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
                 if (numBullets > 3){
                     GUI.DrawTexture (Rect ( screenPosY -60, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
                     if (numBullets > 4){
                         GUI.DrawTexture (Rect ( screenPosY -80, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
                         if (numBullets > 5){
                             GUI.DrawTexture (Rect ( screenPosY -100, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
                             if (numBullets > 6){
                                 GUI.DrawTexture (Rect ( screenPosY -120, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
                                 if (numBullets > 7){
                                     GUI.DrawTexture (Rect ( screenPosY -140, screenPosX,  shell.width, shell.height), shell, ScaleMode.ScaleToFit, true);
                                 }
                             }
                         }        
                     }
                 }
             }
         }
     }    
 
 }

the gray shells part is only to show an empty.

Thank you in advance for the help