and the wand displaces a little beer, so when you fill to the rim of the bottle, removing the wand leaves you the proper headspace for bottle conditioning/carbonation.
and the beer won't flow from the tap at first unless you have the wand's plunger depressed.
I also wouldn't open the tap all the way. a little more than half gives a quick but easy to control bottle fill. too fast and you'll overflow several, wasting beer.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10