Having problems understanding how to set menu values such as fontHeight, y offset, etc.

On the page here: http://www.espruino.com/graphical_menu it describes how to set the height of the font being used, the y offset and so on. However, I've not been able to make the changes to the default values take place. So where in the example menu on that page should they be inserted?

Also, am I right in assuming the y offset changes where the top of the menu will be on the screen?

Thanks in advance.