Function won't be called

I have a method that takes the amount of time that has passed from the Timer script that I have and decrease the spawn time by seconds. But when I run, the float does not decrease.

My spawn code

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class Cubes : MonoBehaviour {
     public float delay = 2f;
     public GameObject cubes;
     public Timer timer;
 
     // Use this for initialization
     void Start () {
         InvokeRepeating ("Spawn", delay, delay);
         GameObject time = GameObject.Find("Timer");
         timer = time.GetComponent<Timer>();
     }
     
     // Update is called once per frame
     void Spawn () {
         Instantiate(cubes, new Vector3 (Random.Range(-6, 6),10,0),Quaternion.identity);
     }
 
     void Update ()
     {
         if (timer.timer % 10 == 0) {
             MinusDelay ();
         }
     }
 
     public void MinusDelay () {
         if (delay <= 0.1f) {
             delay -= 0.1f;
         }
     }
 }
 

Timer code (The Cubes script is attached to the MainCamera)

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class Timer : MonoBehaviour {
 
     public float seconds = 0.0f;
     public float timer = 0.0f;
     public int minuteCount= 0;
     public int hourCount = 0;
     public Text text;
     public GameObject delayer;
 
     // Use this for initialization
     void Start () {
         text = GetComponent<Text> ();
     }
 
     // Update is called once per frame
     void Update () {
         timer += Time.deltaTime;
         seconds += Time.deltaTime;
         text.text = hourCount + ":" + minuteCount + ":" + seconds;
 
         if (seconds >= 60) {
             minuteCount++;
             seconds = 0;
         } 
         else if (minuteCount >= 60) {
             hourCount++;
             minuteCount = 0;
         }
 
     }
 
     void DeActivate () {
         gameObject.SetActive (false);
     }
 }