Why when using Time.timeScale to make a slowdown effect it's changing the resolution to full screen?

Question

The script is attached to empty GameObject :

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SlowDown : MonoBehaviour
{
    [Range(0,0.25f)]
    public float isTime = 0.25f;

    private void Update()
    {
        Time.timeScale = isTime;
    }
}

Once running the game it's slowing down but also make it a full screen :

Answer 1

It isn't. You have this button toggled on: