Update not updating numbers fast enough

I am starting to learn Unity, so I made a "Clicker" kind of game that uses the keyboard instead. My CSharp script is like this

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class Score : MonoBehaviour {
 
     public Text yourScore;
     public int score;
     public Button clickMe;
     public int counter1;
     public int purchased1;
 
     void Start () {
         score = 0;
         Debug.Log(Time.fixedDeltaTime.ToString());
     }
     void Update () {
         yourScore.text = "Money: " + score.ToString();
         if (Input.GetKeyDown(KeyCode.C))
         {
             score++;
         }
         if(score>= 100&& Input.GetKeyDown(KeyCode.K))
         {
             purchased1++;
             score = score - 100 ;
             Debug.Log(purchased1);
         }
         if (counter1 >= 500)
         {
             score++;
             counter1 = counter1 - 500;
         }
     }
     void FixedUpdate()
     {
         counter1 = counter1 + (1 * purchased1);
     }
 }

The problem is that when purchased1 is a really big number (like 1000) counter1 starts to have a "backlog" of numbers. What I mean is that counter1 will stay with ex. 35000 and will slowly start substracting the 500 and adding 1 to score. Can I make it so the process of substracting is faster? I have tried putting it in FixedUpdate and Update with no luck. Thanks in advance.