//SeenMediaDatabase.cs
        public Task<int> CountItemAsync(string column)
        {
            return database.Table<SeenMediaEntry>().Where(i => i.Media == column).CountAsync();
        }

//StatsPage.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using SeenMedia.Data;
using Xamarin.Forms.Xaml;

namespace SeenMedia
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class StatsPage : ContentPage
    {
        public StatsPage()
        {
            InitializeComponent();
        }

        protected override async void OnAppearing()
        {
            base.OnAppearing();
            var Counter = await App.Database.CountItemAsync("Muzeum");
            BooksLabel.Text = Counter.ToString();    <-- Tutaj zmieniasz wartość tekstu na kontrolce "BooksLabel"
        }
    }
}

//StatsPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:SeenMedia"
             x:Class="SeenMedia.StatsPage"
             Title="Twoje statystyki">
    <Label Text="Przeczytałeś tyle książek:"
           VerticalOptions="Center"
           HorizontalOptions="Center" />
    <Label x:Name="BooksLabel"                  <-- Tutaj ustalasz nazwę dla kontrolki
           TextColor="Black"
           VerticalOptions="Center"
           HorizontalOptions="Center" />
</ContentPage>