Xamarin.Forms XAML에서 Margin의 위, 아래, 왼쪽 및 오른쪽 순서

<?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:MarginTest" 
        x:Class="MarginTest.MarginTestPage" 
        BackgroundColor="Silver">

    <BoxView 
        Margin="10, 20, 30, 40"
        BackgroundColor="Red"
        HorizontalOptions="FillAndExpand" 
        VerticalOptions="FillAndExpand" />

</ContentPage>

// syntax
public Thickness (Double left, Double top, Double right, Double bottom)