Integer gets too many additions

I wrote a quick combo script but the if statement gives the combo a value of about 14 as opposed to 1. I think that the problem is that it checks every frame. Is there a way that it can only check that for 1 frame?

My code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ComboSystem : MonoBehaviour {

	//Hit Types
		public bool NormalAttack;
		public bool ChargedAttack;
		public bool DashAttack;
	
	//Combo Timer Variables
		public float ComboTime; 
		public float ComboTimer; 
	
	//Combo Variables
		public int Combo;
	
	void Update() {
		//Hit references
			NormalAttack = this.gameObject.GetComponent<AttackControls>().NormalAttack;
			ChargedAttack = this.gameObject.GetComponent<AttackControls>().ChargedAttack;
			DashAttack = this.gameObject.GetComponent<AttackControls>().DashAttack;
		
		//Combo Timers
			if(NormalAttack == true || ChargedAttack == true || DashAttack == true) {
				ComboTime = ComboTimer;
				Combo += 1;
			}
			
			if(ComboTime > 0){
				ComboTime -= Time.deltaTime;
			}
			if(ComboTime < 0){
				ComboTime = 0;
			}
			if(ComboTime == 0){
				Combo = 0;
			}
	}
}

Dont really understand what u wants, but Update is being called once in every frame, if you want something to run in every 14th frame then you should use a Coroutine also what u wrote is also should be a Coroutine.
to start a Coroutine in unity use StartCoroutine(RoutineName);

private IEnumerator ICombat()
    {
        //do something
        yield return new WaitUntil(this_is_a_predicate_which_waits_until_14th_frame);
    }

@RobertVanDerLeeuw

It seems that your variables NormalAttack or ChargedAttack or DashAttack remain true for more than 1 update frame, that is why you get a value of 14 instead of 1.

Try incrementing the “Combo” value at the instance where you are updating the boolean variables to true (If the latter is not in Update)