How to use this script for a depleting fuel bar as you thrust with a rocket

using UnityEngine;
using System.Collections;

 public class Progress : MonoBehaviour {
     public float barDisplay; //current progress
     public Vector2 pos = new Vector2(20,40);
     public Vector2 size = new Vector2(60,20);
     public Texture2D emptyTex;
     public Texture2D fullTex;
 
     void OnGUI() {
     //draw the background:
     GUI.BeginGroup(new Rect(pos.x, pos.y, size.x, size.y));
         GUI.Box(new Rect(0,0, size.x, size.y), emptyTex);
     
         //draw the filled-in part:
         GUI.BeginGroup(new Rect(0,0, size.x * barDisplay, size.y));
             GUI.Box(new Rect(0,0, size.x, size.y), fullTex);
         GUI.EndGroup();
     GUI.EndGroup();
 }
 
 void Update() {
         //for this example, the bar display is linked to the current time,
         //however you would set this value based on your desired display
         //eg, the loading progress, the player's health, or whatever.
         barDisplay = Time.time*0.05f;
//       barDisplay = MyControlScript.staticHealth;
    }
}

So this code is from another question response on this site itself. Im a newb, so i could use some help. If i just use it as is, attach it to my rocket gameobject and set the float fuel = barDisplay it only depletes the bar after the fuel bar hits 0, which coincidentally is the point in my code that i disable the thrusting movement function and invoke my Death() after a few seconds just in case the player is on a friendly platform like the launcher in my game.

I think that you need to edit your script a bit. So 1) replace your texture 2d with images or just make another variables 2) Then just make your filled image of type “Filled” 3) yourImage.fillAmount = some float decreasing its value over time 4) make a float :

Ienumerator decrese() {
Yield return new waitForSeconds (0.5f)
YourFloat - = some decrease value
}
5) Start corutine in Update method : StartCorutine(decrese() )

Hope it helps