Rolex Yacht-Master II Watch: how to use the programmable countdown

Here is some information on how to use the programmable countdown function of the Rolex Yacht-Master II watch:

From Rolex website:
"The Yacht-Master II features an exclusive function developed by Rolex: a countdown which can be programmed from 1 to10 minutes and incorporates a mechanical memory, allowing it to be reset to the same countdown duration. Once launched, it can also be synchronized on the fly, enabling it to be adjusted to match the official regatta countdown. The countdown function responds ideally to the need for precise timing during the crucial starting sequence of a regatta. Although technically complex, it is essentially very simple to use: the countdown is programmed via the rotatable Ring Command bezel, an innovative interface between bezel and movement developed by Rolex."