FWIW most articles I'm finding source the $660M number to the linked Tuoi Tre News story. Their quote is "The victims said the company had conned them out of VND15 trillion (US$660.79 million)." https://tuoitrenews.vn/news/business/20180409/vietnamese-cry...
I have no doubt there was yet another ICO scam with someone walking away with the money, but I wonder how much money it was.