You can also initiate RTH by turning the controller off like with previous models of phantom.
It's invariably best to cancel RTH and reconnect to land manually when it is back in good visual range.
The GPS can easily be 10-20 feet out and it descends quite rapidly in auto land. 

You need to (gently) hold the button for maybe 3 seconds, I suppose this is so you can't accidentally do it.
The screen will show you are in RTH mode.
The Phantom will ascend to the preset altitude - set beforehand! - and turn towards home.
You can yaw from side to side to look about but it will continue in a straight line to Home unless you cancel it when it's closer.