As far as I know, it's about 16,000 BTC. And the network immediately appeared a message to prevent an ambiguous interpretation of this sale.

"Following consultation with cryptocurrency experts, I sold BTC and BCC, not by an ordinary sale through the BTC/BCC exchange, but in a manner that would avoid affecting the market price, while ensuring the security of the transaction to the [greatest] extent possible,"

This is direct quote from Mt. Gox Trustee Kobayashi. As you can see, this transaction can not affect the course of Bitcoin in any way.