Level.cs

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

public class Level : MonoBehaviour
{
    float startTime;
    int numTreasures;
    int collected = 0;

    void Start()
    {
        startTime = Time.time;
        GameObject[] treasureObjects = GameObject.FindGameObjectsWithTag("Treasure");
        numTreasures = treasureObjects.Length;
    }

    void TreasureCollected()
    {
        collected++;
    }

    void OnGUI()
    {
        GUI.skin.label.fontSize = 20;
        GUI.Label(new Rect(10, 10, 200, 30), "Time: " + (Time.time - startTime).ToString("#.##"));
        GUI.Label(new Rect(10, 40, 200, 30), "Treasures: " + collected + "/" + numTreasures);
    }
}