Keep a certain frame within an android app

I'm trying to manipulate the frame rate within a unity scene, when I run it on the unity platform, it works with the given frame value I gave it. However, when I switch it to my phone, it varies from 25 to 30 fps.

- > I already changed the v sync count - > do not use

- > I already changed the frame directly on AndroidUnityPlayer.cs

- > I've already used Time.captureFramerate

- > And I'm using this code to change the frame:

using UnityEngine;
using System.Collections;


public class FPSScript : MonoBehaviour {

    public float updateInterval = 0.5F;
    private float lastInterval;
    private int frames = 0;
    private float fps;

    void Start() {
        lastInterval = Time.realtimeSinceStartup;
        frames = 0;

        Application.targetFrameRate = 10;

    }

    void OnGUI() {
        GUILayout.Label("" + fps.ToString("f2"));
    }

    void Update() {
        ++frames;
        float timeNow = Time.realtimeSinceStartup;
        if (timeNow > lastInterval + updateInterval) {
            fps = frames / (timeNow - lastInterval);
            frames = 0;
            lastInterval = timeNow;
        }
    }
}