test/Assets/scrpts/Counter.cs

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

public class Counter : MonoBehaviour
{
    public int total;

    private Text txt;
    void Start()
    {
        total =0;
        txt = this.GetComponent<Text>();
    }

    void Update()
    {
        txt.text = total.ToString();
    }
}