issue with bullet hole decal

I hope you can help me with this issue, as you can see in the image that i've attached below, when my bullet hits the wall (i'm using a raycast) a bullet hole decal is instantiated, but when the bullet hit wall really close to the edge, the decal looks ugly, the decal is out of the edge.

does anybody know how to solve this issue?

here is my code

 var speed:float=500;
 var lifeTime:float=3;
 var bulletGravity:float=9.8;
 var decalHitWall:GameObject;
 var dustParticle:GameObject;
 var floatInFrontOfWall : float = 0.01;
 @HideInInspector
 var moveDirection: Vector3;
 @HideInInspector
 var shortestSoFar: float;
 @HideInInspector
 var instantiatePoint:Vector3;
 @HideInInspector
 var instantiateRotation: Quaternion;
 @HideInInspector
 var foundHit: boolean=false;
 @HideInInspector
 var parentToAdd :Transform;
 @HideInInspector
 
 
 function Awake()
 {
   transform.Rotate(0,0,0);
   moveDirection=transform.forward*speed;
   shortestSoFar=Mathf.Infinity;
   foundHit=false;
   
 }
 
 function Update()
 {
   transform.rotation=Quaternion.LookRotation(moveDirection);
   var hits: RaycastHit[];
   hits=Physics.RaycastAll(transform.position,transform.forward,speed*Time.deltaTime);
   for(var hit in hits)
   {
     if(hit.transform.tag=="Level Parts")
     {
       if(Vector3.Distance(transform.position,hit.point)<shortestSoFar)
       {
           instantiatePoint=hit.point+(hit.normal * (floatInFrontOfWall+Random.Range(0,0.001)));
         instantiateRotation=Quaternion.LookRotation(hit.normal);
         parentToAdd=hit.transform;
         shortestSoFar=Vector3.Distance(transform.position,hit.point);
         foundHit=true;
         
       }
     
     }
   }
   
   if(foundHit)
   {
       var SpawnBulletHole: GameObject = Instantiate(decalHitWall,instantiatePoint,instantiateRotation);
       Instantiate(dustParticle, instantiatePoint,instantiateRotation);
       if(parentToAdd)
           SpawnBulletHole.transform.parent=parentToAdd;
     Destroy(gameObject);}
     
     transform.position+=moveDirection*Time.deltaTime;
     //moveDirection.y-=bulletGravity*Time.deltaTime;
     lifeTime-=Time.deltaTime;
     if(lifeTime<0)
     {
        Destroy(gameObject);
     }
     
   
   
 }
 

][1]