New featured Pointers options

Hi,

I can′t find a complete documentation of how this new feature works. I have two questions:

1) How this parameters works:

position: {
		            my: 'left top',
		            at: 'left top',
		            offset: '10 30'
		        },
		        arrow: {
		            edge: 'left',
		            align: 'left',
		            offset: 0
		        },
		close: function() {
			setUserSetting( 'p1', '1' );
		}

i.e. How can I move the arrow to the left size but in the left border not un the top border. What is the difference between my: and at:?

2) Seems does not work in the Custom Post Types?

Thanx for any help ??