Full report (PDF) here
To summarise, all those jewellery shops around the casinos in Macau? They're processing massive amounts of fraudulent UnionPay cash withdrawals, processed as 'generic sales' - or in some cases 'selling' bullion then buying it back immediately for cash, which amounts to the same thing - as a way of getting around China's money transfer limitations. UnionPay is relatively lightly regulated in China, since it's seen as a successful national brand and a soft power export, and there are cracks in regulation between Macau and Chinese authorities. The report talks about the money going to the casinos, but there's a slightly disguised implication that it could be used for large-ish scale money laundering as well...