Calculating percentage in code is reversed?

Hi, I have a script here that calculates the percentage between two numbers, but it's in reverse. Reverse as in 0 is seen as 100% of 100 instead of the other way around. (100 being 100% of 100).

Does this have to be written in a specific way?

 using UnityEngine;
 using System.Collections;
 
 public class percentagetest : MonoBehaviour 
 {
     public float maxValue;
     public float currentValue;
     private float finalValue;
 
     void Update () 
     {
         finalValue = (maxValue - currentValue) / maxValue * 100;
         //Calculate percentage
     }
 
     void OnGUI ()
     {
         GUI.Label(new Rect(5,5,250,250),finalValue.ToString());
         //Display result
     }
 }