Problem with loading bar creation

Hi, I’m trying to a colour changing progress bar but I’ve been facing some problems.
attached below is the code and a link to video showcasing the hierarchy & game object component settings, thanks.
https://drive.google.com/file/d/1ghNGaHAHM4PTm5ta_JNVogsAIK3-ecN_/view?usp=sharing

using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using Microsoft.Unity.VisualStudio.Editor;
using UnityEngine;


public class ProgressBar : MonoBehaviour
{
    public int maxAmount;
    public int currentAmount;
    public UnityEngine.UI.Image mask;
    public UnityEngine.UI.Image fills;
    public Color normal;
    public Color lowSpace;
    public Color full;
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        calculate();
    }
    void calculate()
    {
        float percentage = (float)currentAmount / (float)maxAmount;
        mask.fillAmount = percentage;
        
        if(currentAmount<maxAmount*70/100)
        {
            fills.color = normal;
        }
        else if (currentAmount > maxAmount * 69 / 100 && currentAmount < maxAmount * 89 / 100)
        {
            fills.color = lowSpace;
        }
        else if (currentAmount > maxAmount * 90 / 100)
        {
            fills.color = full;
        }


    }
}