OnTriggerEnter2D is being called multiple times....

I'm new to Unity so sorry in advance if this is a basic question, I attached a variable that should add by 1 every time OnTriggerEnter2D is triggered. It however is not adding by 1 but adding constantly. Can please tell me what I'm doing wrong?

Here is where I'm calling it

 public class MonsterTarget : MonoBehaviour {
     public Resetter Resetting;
     public ScoreCount ScoreHit;
     public float targetHit = 0;
  
     
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 
     public void OnTriggerEnter2D(Collider2D col)
     {
         targetHit ++;
         Resetting.Reset();
         
     }
 }
 

and this is where its going

 public MonsterTarget monTarget;
 
     public Text scoreText;
     public Text highScoreText;
 
     public float scoreCount;
     public float highScoreCount;
 
     public bool scoreIncreasing;
 
     // Use this for initialization
     void Start () {
         if(PlayerPrefs.HasKey("HighScore"))
             {
             highScoreCount = PlayerPrefs.GetFloat("HighScore");
         }
     }
     
     // Update is called once per frame
     void Update () {
         if (scoreIncreasing)
         {
             scoreCount += monTarget.targetHit;//RIGH HERE IS WHERE IM CALLING IT
         }
 
         if (scoreCount > highScoreCount)
         {
             highScoreCount = scoreCount;
             PlayerPrefs.SetFloat("HighScore", highScoreCount);
         }
 
         scoreText.text = "Score: " + Mathf.Round(scoreCount);
         highScoreText.text = "High Score: " + Mathf.Round(highScoreCount);
 
     }
 }