Yeah, I'm not entirely sure how they managed to get on BitcoinAverage. As far as I know, they don't have an API that exposes trade-volume. And they're not an actual exchange either, they primarily just follow Bitstamp prices with some of their profit margin added on top.
They have their own
exchange which is about to go live as soon as they get permission from the Dutch Central Bank, which should be somewhere in February. In the meantime they are running with a closed group of traders, which is allowed.