Why is this just printing 1?

gistfile1.txt

            var scheduler = new TestScheduler();

            var source = scheduler.CreateHotObservable(
              new Recorded<Notification<int>>(600, Notification.CreateOnNext(1)), 
              new Recorded<Notification<int>>(1200, Notification.CreateOnNext(2)),
              new Recorded<Notification<int>>(1600, Notification.CreateOnNext(3)),
              new Recorded<Notification<int>>(2000, Notification.CreateOnNext(4)),
              new Recorded<Notification<int>>(2400, Notification.CreateOnNext(5)),
              new Recorded<Notification<int>>(3000, Notification.CreateOnNext(6)),
              new Recorded<Notification<int>>(3500, Notification.CreateOnNext(7))
              );

            var my = source
                         .Window(() => Observable.Timer(TimeSpan.FromMilliseconds(500)))
                         .SelectMany(x => x.Take(1));

            my.Subscribe(Console.WriteLine);

            scheduler.AdvanceTo(3500);
            
            Console.ReadLine();