Understanding Grid Layout

I am a bit confused about the Add method of Grid with four args:

grid.Children.Add(new Label
{
Text = "Span two rows (or more if you want)",
TextColor = Color.Yellow,
BackgroundColor = Color.Navy,
XAlign = TextAlignment.Center,
YAlign = TextAlignment.Center
}, 2, 3, 1, 3);

Can anybody tell me what exactly each parameter represents; especially 2nd and 4th ones?
I assume 1st and 3rd args are column and row numbers respectively but what about 2nd (int right) and 4th (int bottom) args?