Trying stuff with the Rogue tutorial

Hello,
I wanted to try a personnal Tileset with the tutorial project Rogue, but my tileset is way bigger. I know how to reduce my tileset, but i would like to increase the base resolution of the tiles.

In this tutorial, we never define the base size of a tile.

I tried to look into the Board Manager script what could define this but I dont get it.
And there is no grid created outside of the script.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using System;
4. using UnityEngine;
5. using Random = UnityEngine.Random;
6.  
7. public class BoardManager : MonoBehaviour
8. {
9.     [Serializable]
10.     public class Count
11.     {
12.         public int minimum;
13.         public int maximum;
14.  
15.         public Count (int min, int max)
16.         {
17.             minimum = min;
18.             maximum = max;
19.         }
20.     }
21.  
22.     public int columns = 8;
23.     public int rows = 8;
24.     public Count wallCount = new Count(5, 9);
25.     public Count foodCount = new Count(1, 5);
26.  
27.     public GameObject exit;
28.     public GameObject[] floorTiles;
29.     public GameObject[] outWallTiles;
30.     public GameObject[] wallTiles;
31.     public GameObject[] enemyTiles;  
32.     public GameObject[] foodTiles;
33.  
34.     private Transform boardHolder;
35.     private List<Vector3> gridPositions = new List<Vector3>();
36.    
37.     void InitialiseList()
38.     {
39.         gridPositions.Clear();
40.  
41.         for (int x = 1; x < columns - 1; x++)
42.         {
43.             for (int y = 1; y < rows - 1; y++)
44.             {
45.                 gridPositions.Add(new Vector3(x, y, 0f));
46.             }
47.         }
48.     }
49.  
50.     void BoardSetup ()
51.     {
52.         boardHolder = new GameObject("Board").transform;
53.  
54.         for (int x = -1; x < columns + 1; x++)
55.         {
56.             for (int y = -1; y < rows + 1; y++)
57.             {
58.                 GameObject toInstantiate = floorTiles[Random.Range(0, floorTiles.Length)];
59.  
60.                 if (x == -1 || x == columns || y == -1 || y == rows)
61.                     toInstantiate = outWallTiles[Random.Range(0, outWallTiles.Length)];
62.                 GameObject instance = Instantiate(toInstantiate, new Vector3(x, y, 0f), Quaternion.identity) as GameObject;
63.  
64.                 instance.transform.SetParent(boardHolder);
65.             }
66.         }
67.     }
68.  
69.     Vector3 RandomPosition()
70.     {
71.         int randomIndex = Random.Range(0, gridPositions.Count);
72.         Vector3 randomPosition = gridPositions[randomIndex];
73.         gridPositions.RemoveAt(randomIndex);
74.         return randomPosition;
75.     }
76.  
77.     void LayoutObjectAtRandom(GameObject[] tileArray, int minimum, int maximum)
78.     {
79.         int objectCount = Random.Range(minimum, maximum + 1);
80.         for (int i = 0; i < objectCount; i++)
81.         {
82.             Vector3 randomPosition = RandomPosition();
83.             GameObject tileChoice = tileArray[Random.Range(0, tileArray.Length)];
84.             Instantiate(tileChoice, randomPosition, Quaternion.identity);
85.         }
86.     }
87.     public void SetupScene(int level)
88.     {
89.         BoardSetup();
90.         InitialiseList();
91.  
92.         LayoutObjectAtRandom(wallTiles, wallCount.minimum, wallCount.maximum);
93.  
94.         LayoutObjectAtRandom(foodTiles, foodCount.minimum, foodCount.maximum);
95.  
96.         int enemyCount = (int)Mathf.Log(level, 2f);
97.         LayoutObjectAtRandom(enemyTiles, enemyCount, enemyCount);
98.  
99.         Instantiate(exit, new Vector3(columns - 1, rows - 1, 0f), Quaternion.identity);
100.     }
101. }
102.