Grid Snapping Problem

I have a code below. I want to make a grid placement system like Mad Games Tycoon etc. It's working but objects snapping middle of 4 grid like this how can i fix it?.

     public Vector3 tileWorld;
     public Vector3 pos;
     public float gridRadius;
     public float outline;
     public GameObject sad;
     public GameObject quad;
 
     private void Awake()
     {
         CreateGrids();
     }
 
     private void Update()
     {
         pos.x = Mathf.Floor(sad.transform.position.x / gridRadius) * gridRadius;
         pos.y = Mathf.Floor(sad.transform.position.y / gridRadius) * gridRadius;
         pos.z = Mathf.Floor(sad.transform.position.z / gridRadius) * gridRadius;
         sad.transform.position = new Vector3(pos.x, sad.transform.position.y, pos.z);
     }
 
     void CreateGrids()
     {
         for (int x = 0; x < tileWorld.x; x++)
         {
             for (int z = 0; z < tileWorld.z; z++)
             {
                 Vector3 tilePosition = new Vector3(-tileWorld.x / 2 + gridRadius + x, 0, -tileWorld.z / 2 + gridRadius + z);
                 GameObject newTile = Instantiate(quad, tilePosition, Quaternion.Euler(Vector3.right * 90)) as GameObject;
                 newTile.transform.position = new Vector3(newTile.transform.position.x, 0.5f, newTile.transform.position.z);
             }
         }
     }