How do I display text with Countdown Timer Minutes and Seconds

I trying to display the the text time with the countdown timer on scene . I gotten an error CS0119
I want the timer text to look like this when the scene is on play Time : 2:38 , Time : 2:37 , like this. Here is some of my code.

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
public class clock : MonoBehaviour
{

  Text text;
  public int Minutes;
  public int Seconds;

  private float realMinutes ;
  private float realSeconds ;

  public void Start()
  {
       text = GetComponent <Text> ();
	   realMinutes = Minutes ;
       realSeconds = Seconds ;
  }

 void Update () 
 { 
        		 text.text = "Time:" + Time;
	 realMinutes -= Time.deltaTime;
     realSeconds -= Time.deltaTime;

            Minutes = (int) realMinutes ;
            Seconds = (int) realSeconds ;
 }

}

You can try with the next class;

using UnityEngine;
using UnityEngine.UI;

public class MyClock : MonoBehaviour
{
    public int  Minutes = 0;
    public int  Seconds = 0;

    private Text    m_text;
    private float   m_leftTime;

    private void Awake()
    {
        m_text = GetComponent<Text>();
        m_leftTime = GetInitialTime();
    }

    private void Update()
    {
        if (m_leftTime > 0f)
        {
            //  Update countdown clock
            m_leftTime -= Time.deltaTime;
            Minutes = GetLeftMinutes();
            Seconds = GetLeftSeconds();

            //  Show current clock
            if (m_leftTime > 0f)
            {
                m_text.text = "Time : " + Minutes + ":" + Seconds.ToString("00");
            }
            else
            {
                //  The countdown clock has finished
                m_text.text = "Time : 0:00";
            }
        }
    }

    private float GetInitialTime()
    {
        return Minutes * 60f + Seconds;
    }

    private int GetLeftMinutes()
    {
        return Mathf.FloorToInt(m_leftTime / 60f);
    }

    private int GetLeftSeconds()
    {
        return Mathf.FloorToInt(m_leftTime % 60f);
    }
}