Timer doesn't sync with slideshow

Questions & Answers
1

I am still new to unity and recently I want to build a timer attached to a slideshow for further design. But I found out that somehow the time of the timer always fall behind the time of the slideshow changing about 2.5 seconds. Any help will be appreciated.

using UdonSharp;
using UnityEngine;
using VRC.SDKBase;
using VRC.Udon;
using UnityEngine.UI;

public class exp : UdonSharpBehaviour
{
    public Sprite[] spriteList = new Sprite[10];
    public SpriteRenderer spriteRenderer;
    public float[] times = new float[10];
    [HideInInspector]
    public float[] y;
    public Renderer rend;
    public Collider sphere;
    [HideInInspector]
    public int page = 0;
    public Text display;
    private float time = 0f;
    public bool playing = false;
    private bool timerplaying = false;
    public override void Interact()  //button interact//
    {
        time = 0f;
        playing = true;
        page = 0;
        rend = GetComponent<Renderer>();
        sphere = GetComponent<Collider>();
        rend.enabled = false;
        sphere.enabled = false;
        y = times;
        timerplaying = true;
    }

    private void FixedUpdate()   //slideshow move + timer move//
    {
        if (!playing) return;
        if (!timerplaying) return;
        time += Time.deltaTime;
        if (y[page] > 0f)
        {
            y[page] -= Time.deltaTime;
            display.text = "Timer: " + y[page].ToString("F1");
        }
        else
        {
            page++;
        }
        if (playing == true && time > times[page] && page < spriteList.Length)
        {
            page++;
            spriteRenderer.sprite = spriteList[page];
            time = 0f;
        }

    }
}
2

You are making it unnecessarily complex, with the risk of missing something, maybe this is better (note the use of Time.fixedDeltaTime in FixedUpdate):

private void FixedUpdate()
{
    if (!playing) return;
    if (!timerplaying) return;
    y[page] -= Time.fixedDeltaTime;
    if (y[page] > 0f)
    {
        display.text = "Timer: " + y[page].ToString("F1");
    }
    else
    {
        if(page < spriteList.Length) {
            page++;
            spriteRenderer.sprite = spriteList[page];
        }
    }
}