Multiplicity numbers

using System;

internal class Program
{
    static void Main(string[] args)
    {
        Random random = new Random();
        int minNumberN = 1;
        int maxNumberN = 27;
        int startNumber = 100;
        int finishNumber = 999;
        int numberN = random.Next(minNumberN, maxNumberN + 1);
        int quantity = 0;

        for (int i = startNumber; i <= finishNumber; i+=numberN)
        {
            if (i >= startNumber)
            {
                quantity++;
            }
        }
        Console.WriteLine(numberN);
        Console.WriteLine(quantity);
    }
}