I am creating a castle defense game where the enemy regulary spawns (upto limit of 24 ). After the enemy reaches 24, I want to stop creating clones. So far, I have been successful but I want to make sure that if the enemy reaches 23, it starts instantiating upto 24. How?

    public GameObject[] spawnPosition;
    public GameObject enemy;
    [SerializeField]
    private float startTime;
    private float timeForSpawn;
    public float speed;
    public float enemyLimit;
    public List<GameObject> enemyList;
    public bool stopInstantiating;
    void Start () {
        stopInstantiating = false;
        enemyList = new List<GameObject> ();
        enemyLimit = 24f;
        timeForSpawn = startTime;
    }


    void Update () {
        
        Spawn ();
    }

    void Spawn () {

        timeForSpawn -= Time.deltaTime;
        if (timeForSpawn <= 0 && stopInstantiating == false) {
            timeForSpawn = startTime;
                for (int i = 0; i <= 2; i++) {
                Instantiate (enemy, spawnPosition [i].transform.position, Quaternion.identity);
                if (enemy != null&& stopInstantiating == false) {
                    enemyList.Add (enemy);
                    if (enemyList.Count >= enemyLimit) {
                        stopInstantiating = true;
                } 
                }
            }
        }
}

}

I see that the list doesn't update itself as I delete the gameObjects in game. How to make sure that list updates and work on that.