Short selling and algo trading on exchanges would get counted towards that volume ?
With the exchange scams going around daily o wouldn't be surprised if that number is order of magnitude higher than the actual USD involved and in trading.
If I use 1 million dollars to make 1000 trades in and out of btc in a day that's a billion dollars of volume but maybe a couple of million in market depth could make that stable to enable those trades and a couple mill more could crash it.
With the exchange scams going around daily o wouldn't be surprised if that number is order of magnitude higher than the actual USD involved and in trading.