Having trouble adding offsets to my grid

I would like to add some offsets to my points in my grid but I don't know how. I made it where it had to generate a grid full of cubes from the center but ever since adding that I am unable to figure out how to implement the offset part, I'm trying to do this in the pic.

Example Pic:

Code:

 public class Grid : MonoBehaviour {
 
     public Vector3[] points;
 
     public int xSize = 5;
     public int zSize = 5;
     public float offset = 1;
     // Use this for initialization
     void Start () {
 
         points = new Vector3[zSize * xSize];
 
         for(int i = 0, z = 0; z < zSize; z++)
         {
             for (int x = 0; x < xSize; x++, i++)
             {
                 points[i] = new Vector3(x - (xSize / 2f), z - (zSize / 2));
                 print("There are " + points[i]);
             }
         }
         
     }
     private void OnDrawGizmos()
     {
         Gizmos.color = Color.black;
         for (int i = 0; i < points.Length; i++)
         {
             Gizmos.DrawSphere(points[i], 0.1f);
         }
     }
 
     // Update is called once per frame
     void Update () {
         
     }
 }