Referencing other scripts: -5 seconds rule on timer

Hello Unity Users, I need help with my game timer. In my game, when the ball hits the finishline trigger, what is suppose to happen is:

• The ball is destroyed

• minus 5 seconds from the Count-Up timer

I dont know why its giving me problems. I am referring The timer from my working timer script into my finishline script. I keep getting this error.

Assets/Scripts/Finishline.cs(30,32): error CS0120: An object reference is required to access non-static member `Clock2.OnGUI()'

Please Help! Novice Unity User

 public class Finishline : MonoBehaviour 
 {
 //declare scoring variables
     public int count;
     public GUIText countText;
     //Script Reference
     public int Clock2.OnGUI.Dseconds;
     public Clock2 Timer;
 
     void Start () 
     {
         count = 0;
         SetCountText();
     }
 
 //if the balls collides with a finishline collider, finishline destroys the balls and add a point to score.
         
     void OnTriggerEnter2D(Collider2D other)
     {
         if (other.gameObject.tag == "Ball") 
         {
             Debug.Log ("Object Entered the trigger");
             count += 1;
 
             // subtract 5 seconds whenever a ball enters the finishline
             Clock2.OnGUI().Dseconds = -5;
             SetCountText ();
             //gameObject.SetActive(false);
             Destroy (other.gameObject);
         }
         if (count > 12) 
         {
                 Time.timeScale = 0;
                 
         }
     }
 
     void SetCountText()
     {
         countText.text = "Number of Balls Collected: "+ count.ToString();
         //if(count>11)
         //    {
         //    winText.text = "You Win!";
         //    }
     }
     
 }