Inventory slots number are wrong

So I got a code for an inventory system. However something is wrong. Here's the code:

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class Inventory1 : MonoBehaviour {
 
 
     public List<GameObject> Slots = new List<GameObject> ();
     public List<Item> Items = new List<Item> ();
     public GameObject slots;
     ItemDatabase database;
     int x = -200;
     int y = 195;
 
     // Use this for initialization
     void Start () {
 
         int Slotamount = 0;
 
         database = GameObject.FindGameObjectWithTag ("Item Database").GetComponent<ItemDatabase> ();
 
         for (int i = 1; i < 7; i++) {
             for(int k = 1; k < 4; k++){
                 GameObject slot = (GameObject)Instantiate(slots);
                 slots.GetComponent<SlotsScript>().slotNumber = Slotamount;
                 Slots.Add (slot);
                 Items.Add (new Item());
                 slot.transform.parent = this.gameObject.transform;
                 slot.name = "slot" + " " + i + "." + k;
                 slot.GetComponent<RectTransform>().localPosition = new Vector3(x,y,0);
                 x = x + 385;
                 if(k == 2){
                     x = -200;
                     y = y - 78;
                 }
                 Slotamount++;
             }
         }
 
         AddItem (0);
         AddItem (1);
 
     }
 
     void AddItem(int id){
         for (int i = 0; i < database.items.Count; i++) {
             if(database.items[i].itemID == id){
                 Item item = database.items[i];
                 AddItemAtEmptySlot(item);
                 break;
             }
         }
     }
 
     void AddItemAtEmptySlot(Item item){
         for (int i = 0; i < Items.Count; i++) {
             if(Items[i].itemName == null){
                 Items[i] = item;
                 break;
             }
         }
     }
 }
 

That's the inventory code, and here is the slots code:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class SlotsScript : MonoBehaviour, IPointerDownHandler, IPointerEnterHandler{
 
     public Item item;
     Image itemImage;
     public int slotNumber;
     Inventory1 inventory1;
     
     // Use this for initialization
     void Start () {
         inventory1 = GameObject.FindGameObjectWithTag ("Inventory1").GetComponent<Inventory1> ();
         itemImage = gameObject.transform.GetChild (0).GetComponent<Image> ();
     }
     
     // Update is called once per frame
     void Update () {
 
         if (inventory1.Items[slotNumber].itemName != null) {
             item = inventory1.Items[slotNumber].itemName;
             itemImage.enabled = true;
             itemImage.sprite = inventory1.Items[slotNumber].itemIcon;
         } else {
             itemImage.enabled = false;
         }
     }
 
     public void OnPointerDown(PointerEventData data){
         Debug.Log (slotNumber);
     }
 
     public void OnPointerEnter(PointerEventData data){
 
     }
 }
 

Now my problem is that my very first slot, named 1.1 gets the slot number 17. Then my second slot is 0 and so on till the last one that is 16. Because of this when I add items in the inventory, they start adding from the second slot. Can someone help me?