Video Using QualitySettings.SetQualityLevel is very slow taking 10 seconds to update why ?

I'm creating a main menu.
In the Hierarchy on the Canvas attached this script :

Code (csharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.Audio;
6.  
7. public class SettingsMenu : MonoBehaviour
8. {
9.     public AudioMixer audioMixer;
10.  
11.     public void SetVolume(float volume)
12.     {
13.         audioMixer.SetFloat("Volume", volume);
14.     }
15.  
16.     public void SetQuality(int qualityIndex)
17.     {
18.         QualitySettings.SetQualityLevel(qualityIndex);
19.     }
20. }
21.  

Then in he Hierarchy on the Graphics (dropdown ui) I scrolled down and dragged the canvas and selected Dynamic int SetQuality method.

This screenshot show the Canvas with the script attached to it :



And now a screenshot of the Graphics Inspector settings :



Now when running the game I opened the Edit > Project Settings... > Quality to see in real time the changes when changing in the game the Graphics level settings :

Then changed it to LOW and it took about 5-7 seconds to change it to Low sometimes it might taken even more time to change almost 8 seconds more or less.

I can't figure out why it's taking so much time to change it.

A screenshot after changed to LOW and it didn't change it Low in real time it's taking a lot of time :