Why aren't these numbers going down by 1.

Hey. So I got this script to show stamina in my game. It's in C# and I'm not good at it. If found it at a forum and added some bits to it to fit me. One of which is displaying the stamina, at the bottom in GUI. The problem I have is that when I start running the number goes down by decimals and not whole numbers so the whole thing looks weird on screen. How do I make it so it simply goes down 1 by 1 and not in decimals.

 using UnityEngine;
 using System.Collections;
 
 public class StaminaRun : MonoBehaviour
 {
     private float barLength = 0.0f;
     
     // Max running time
     public float RunningTime = 10f;
 
     // How fast do we regenerate available running time?
     public float RestRate = 1f;
 
     // Player must be able to run for at least X seconds
     public float RunThreshold = 2f;
 
     private vp_FPPlayerEventHandler Player;
     public float availableRunTime;
 
     protected virtual void Awake()
     {
 
         // cache the player event handler
         Player = GameObject.FindObjectOfType(typeof(vp_FPPlayerEventHandler)) as vp_FPPlayerEventHandler;
         availableRunTime = RunningTime;
 
     }
 
     /// <summary>
     /// registers this component with the event handler (if any)
     /// </summary>
     protected virtual void OnEnable()
     {
 
         // allow this monobehaviour to talk to the player event handler
         if (Player != null)
             Player.Register(this);
 
     }
 
     /// <summary>
     /// unregisters this component from the event handler (if any)
     /// </summary>
     protected virtual void OnDisable()
     {
 
         // unregister this monobehaviour from the player event handler
         if (Player != null)
             Player.Unregister(this);
 
     }
 
     public void Update()
     {
         if (!Player.Run.Active)
         {
             // If we're not running, regenerate our stamina
             availableRunTime = Mathf.Min(availableRunTime + Time.deltaTime * RestRate, RunningTime);
             return;
         }
 
         // Decrease our running time available and see if we have to stop
         availableRunTime -= Time.deltaTime;
         if (availableRunTime <= 0)
         {
             Player.Run.TryStop();
             availableRunTime = 0;
         }
     }
 
     protected virtual bool CanStart_Run()
     {
         // Only enable running if we're above the running threshold
         if (availableRunTime >= RunThreshold)
             return true;
 
         return false;
     }
     
     void  OnGUI ()
     {
 
     GUI.Box(new Rect(5, 130, 55, 23), "Stamina");
         
     GUI.Box(new Rect(62, 130, barLength, 23), availableRunTime + "/" + 10);
     
     }
     
     void  Start ()
     {
         barLength = Screen.width / 7;
     }
 
 }