XF Serious memory leaks while creating new strings

I'm seeing some serious memory leaks from a simple string formatting operation. I noticed this due my application UI getting slower over time. I decided to create a very simple solution to isolate and test this issue by itself. It would be great to get somebody else opinion. I'm placing the basics for a XF Android project you can run with the memory profiler to see the problem. Not sure why updating a view label will cause memory leaks. Even just creating a string in the thread and not assign it to the label causes memory leaks. What am I doing wrong here? Thanks!

using System;
using Xamarin.Forms;

namespace testMemoryLeaks
{
    public class App : Application
    {
        public App()
        {
            MainPage = new RandomNumbers();
        }
    }
}

using System;

namespace testMemoryLeaks
{
    public static class Data
    {
        public static double LastRandomNumber = 0.0;

        public static void UpdateRandomNumber()
        {
            Random random = new Random();
            var next = random.NextDouble();
            LastRandomNumber = 0 + (next * 1000);
        }
    }
}

using System;
using System.Collections.Generic;
using Xamarin.Forms;
using System.Threading;

namespace testMemoryLeaks
{
    public partial class RandomNumbers : ContentPage
   {
       public Label numberLabel;
       private string someText = "";
       private bool _dataThreadEnabled = true;
        private bool _uiUpdateThreadEnabled = true;

        public RandomNumbers()
        {
            numberLabel = new Label()
            {
                HorizontalOptions = LayoutOptions.Center,
              VerticalOptions = LayoutOptions.Center,
               TextColor = Color.White,
                Text = "Random Numbers",
                FontSize = 24,
               XAlign = TextAlignment.Center
          };

            StackLayout pageStack = new StackLayout
            {
                HorizontalOptions = LayoutOptions.CenterAndExpand,
                VerticalOptions = LayoutOptions.CenterAndExpand,
                Children =
                {
                    numberLabel
               }
           };
           Content = pageStack;
           StartProcessingThreads();
       }

        public void StartProcessingThreads()
        {
            // Data processing:
            ThreadPool.QueueUserWorkItem(state =>
                {
                   // Updates here
                  while (_dataThreadEnabled)
                  {
                       Data.UpdateRandomNumber();
                       Thread.Sleep(20);
                   }
               });

           // UI updating
           ThreadPool.QueueUserWorkItem(state =>
              {
                 Thread.Sleep(3000);

                    // Start loop updating values
                    while (_uiUpdateThreadEnabled)
                    {
                       // Update screen's gauges values only
                       Device.BeginInvokeOnMainThread(() =>
                           {
                              // Update label. This line is what seems to cause the memory leaks ************
                              numberLabel.Text = string.Format("Numbers {0:0.00}", Data.LastRandomNumber);
                          });
                  }
                 Thread.Sleep(25);
              });
        }
   }
}