using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        int qtyordered = 8;

        var students = new List<Item>() { 

                new Item(){ ItemName = "Pen", Qty=5},

                new Item(){ ItemName = "Pen1", Qty=6},

                new Item(){ ItemName = "Pen2", Qty=7},

                new Item(){ ItemName = "Pen3", Qty=8},

            };

        // How to subtract 8 in the list quantyty

        // expected output is 

        //Pen1 0  // 5-8

        //Pen2 3  //6-3

        //Pen3 7

        //Pen4 8

    }

    class Item{

        public string ItemName{get; set;}

        public int Qty{get; set;}

    }

}