Tiny Banner Ad problem?

I have completed a simple app and I am almost ready to go except for the ads. I have added in my banner script and it works in Test Mode. I have been Googling and searching everywhere for a way to change the height of Unity banner ads, but I could not find anything. I have attached my banner ad code as well as a screenshot of the bottom portion of the device simulator so you can see how tiny the banner shows up as. Can anyone tell me how to set a banner ad's size?

     public string gameId = "1234567";
     public string placementId = "bannerPlacement";
     public bool testMode = true;
 
     [SerializeField] BannerPosition _bannerPosition = BannerPosition.BOTTOM_CENTER;
 
     void Start()
     {
         // Initialize the SDK if you haven't already done so:
         Advertisement.Initialize(gameId, testMode);
         StartCoroutine(ShowBannerWhenReady());
 
         // Set the banner position:
         Advertisement.Banner.SetPosition(_bannerPosition);
     }
 
     IEnumerator ShowBannerWhenReady()
     {
         while (!Advertisement.IsReady(placementId))
         {
             yield return new WaitForSeconds(0.5f);
         }
         Advertisement.Banner.Show(placementId);
     }
 }