Camera not Following Inspector's Value (Transform) When Play

Hi, Sorry for this, but I'm newbie. I swear.

I was learning by following the "Project" provided by Unity. The "Roll-a-Ball". Was learning the camera. I followed the video, but with different value. Then, found a problem.

So, with the inspector, I set the Position value with:

Because I wanted the camera view be like this:

But, when I tested it, I hit Play, the value changed by itself:

And the camera position:

The Main Camera is independent in the hierarchy. And the script for the camera:

 using UnityEngine;
 using System.Collections;
 
 public class CameraController : MonoBehaviour {
 
     public GameObject player;
     private Vector3 offset;
 
     void Start () {
 
         offset = transform.position;
   
     }
 
     void Update () {
 
         transform.position = player.transform.position + offset;
 
     }
 }
 

So, how to use the value I set and not changing when I hit play? Thanks, I'm noob, hope you understand XD