Fontainebleau Circuits Explained

Is there somewhere where I can read a comprehensive explanation of circuits in Fontainebleau and what the rules are (e.g. what all of the symbols are and what they mean). The best explanation that I have found so far is this section on the Font Wikipedia page which has no citations and is kind of vague. 

I particularly curious about a paragraph from the Wikipedia page that claims that you start routes by positioning your body with the painted mark at "navel level" and you're allowed to use any holds within reach. Is this really how it works out there? Like routes are defined based on lining up your belly button with a symbol on the wall? I guess climbing is an absurd sport in any context, but that part just seems too whacky to be true.

I'm sure by now the harder boulders all have standardized starts (check bleau.info/) and that's just a general guide for easier problems to keep them 'at the grade'. 

If you had to mark the start holds minimally (IE with a single point of reference), that seems like a reasonable way to do so (though I'd use eye level TBH). The circuits predate the internet/photo guidebooks so it's not like they had photos to cross-reference or mark the start holds on or beta videos to show the official start.

Think less. Climb more.