Roulette Roulette What Does The Double Arrow Mean In Roulette?

What does the double arrow mean in roulette? - roulette roulette

On Wikipedia: Board_depiction_.28American_Roulette.29 http://en.wikipedia.org/wiki/Roulette #

there is a double-boom 00-0 in the representation on the board over. What does this mean and what are the chances?