Unity2D: How to make script randomly pick a point within an object (X-axis)

Hi, is there a way of randomly spawning my objects on the y-axis. You see, I have a spawning script that randomly pick a point within an object (in this case a 3D cube) to spawn in a prefab, however my spawner only works ( randomly pick a point within an object to spawn) on the x-axis and doesn’t spawn in randomly within the y-axis. This short 1 is a representation of what I am explaining. Thank you
This is my spawning script:

   public GameObject enemy;
   public float spawnTime = 2;
 void Start() {  
     InvokeRepeating ("addEnemy", spawnTime, spawnTime);
 }

 void addEnemy() {  
     var x1 = transform.position.x - GetComponent<Renderer> ().bounds.size.x / 2;
     var x2 = transform.position.x + GetComponent<Renderer> ().bounds.size.x / 2;
     // Randomly pick a point within the spawn object
     var spawnPoint = new Vector2 (Random.Range (x1, x2), transform.position.y);
     Instantiate (enemy, spawnPoint, Quaternion.identity);
    }
  }

It looks like you are using the same code to spawn your enemies from the different cubes (one on top one on right).

If that is not the case then your problem is that your code is reversed. What I mean is it should look like this

void addEnemy()
{
    float y1 = transform.position.y - GetComponent<Renderer> ().bounds.size.y / 2;
    float y2 = transform.position.y + GetComponent<Renderer> ().bounds.size.y / 2;
    // Randomly pick a point within the spawn object
    Vector2 spawnPoint = new Vector2 (transform.position.x, Random.Range (y1, y2));
    Instantiate (enemy, spawnPoint, Quaternion.identity);
}

If you are using the same function to add enemies from the top and the right then your code need to look more like this

public GameObject enemy;
public float spawnTime = 2;
public bool fromTop = false;

void Start()
{
    InvokeRepeating ("addEnemy", spawnTime, spawnTime);
}

// this will handle instantiating objects from the top or right
void addEnemy()
{
    Vector2 spawnPoint = new Vector2 (transform.position.x, transform.position.y);

    if (fromTop)
    {
        float x1 = transform.position.x - GetComponent<Renderer> ().bounds.size.x / 2;
        float x2 = transform.position.x + GetComponent<Renderer> ().bounds.size.x / 2;

        // Randomly pick a x point within the spawn object
        spawnPoint.x = Random.Range (x1, x2);
    }
    else
    {
        float y1 = transform.position.y - GetComponent<Renderer> ().bounds.size.y / 2;
        float y2 = transform.position.y + GetComponent<Renderer> ().bounds.size.y / 2;

        // Randomly pick a y point within the spawn object
        spawnPoint.y = Random.Range (y1, y2);
    }
    Instantiate (enemy, spawnPoint, Quaternion.identity);
}