I don't know the volume, however someone entered a

I don't know the volume, however someone entered a market order to buy and the market makers saw there was no one lined up on the ask, so they pulled their ask prices to a higher amount, filled that order and then lowered their asks. They do it whenever they can.

Disclaimer: Of course, all of this is my opinion and you should not make any investment decisions based on my opinion. I have not received any non-public information.