TD spawn more than one enemy

Here is your modified script to fix your problem (please forgive me for reformatting your code)

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class SpawnWave : MonoBehaviour
 {
     public List<Wave> waves = new List<Wave>();
     public List<SubWave> SWave = new List<SubWave>();
     public EnemyMovent enemy;
 
     Wave currentWave;
     SubWave SubWa;
 
     // [HideInInspector] // uncomment this to hide in inspector or remove the public
     public int currentWaveNumber = -1;
 
     // [HideInInspector] // uncomment this to hide in inspector or remove the public
     [Range(2, 20)] // change if needeed
     public int enemiesRemainingToSpawn = 5; // change this to desired value - must be greater than 0
 
     // [HideInInspector] // uncomment this to hide in inspector or remove the public
     public int enemiesRemainingAlive = 0; // needs to default to 0
 
     // [HideInInspector] // uncomment this to hide in inspector or remove the public
     public float nextSpawnTime;
 
     // [HideInInspector] // uncomment this to hide in inspector or remove the public
     [Range(0, 10)] // change if needeed
     public int WaitforSpawn = 5;
 
     void Start()
     {
         nextSpawnTime = Time.time;
         nextSpawnTime = Time.time + 3;
         Invoke("NextWave", WaitforSpawn);
     }
 
     void Update()
     {
         if (currentWave != null)
         {
             if (enemiesRemainingToSpawn > 0 && Time.time > nextSpawnTime)
             {
                 enemiesRemainingToSpawn--;
                 nextSpawnTime = Time.time + currentWave.timeBetweenSpawns;
 
                 EnemyMovent spawnedEnemy = Instantiate(enemy);
                 enemiesRemainingAlive++;
                 
                 // you may want to randomly place the spawned object somewhere on the screen like so
                 // Vector3 position = new Vector3(Random.Range(-9f, 9f), Random.Range(-5f, 5f), 0);
                 // spawnedEnemy.gameObject.transform.position = position;
                 spawnedEnemy.OnDeath += OnEnemyDeath;
             }
         }
     }
 
     void OnEnemyDeath()
     {
         enemiesRemainingAlive--;
         enemiesRemainingToSpawn++;
 
         if (enemiesRemainingAlive == 0)
         {
             Invoke("NextWave", WaitforSpawn);
         }
     }
 
     void NextWave()
     {
         if (currentWaveNumber < waves.Count)
         {
             waves.Add(new Wave());
             currentWaveNumber = waves.Count - 1;
             currentWave = waves[currentWaveNumber];
             enemiesRemainingToSpawn = currentWave.enemyCount;
         }
         currentWaveNumber++;
         print("Wave: " + currentWaveNumber);
     }
 
     [System.Serializable]
     public class Wave
     {
         public List<SubWave> subWave = new List<SubWave>();
         public int enemyCount = 5;          // you need a value here
         public float timeBetweenSpawns = 3; // you need a value here
     }
 
     [System.Serializable]
     public class SubWave
     {
         public EnemyMovent Enemy;
         public int count = 1;
     }
 }

Since I did not have the EnemyMovent class I have to create a dummy one with a delagate for testing purposes.