I was able to sell 1 million of my shares today...

I was able to sell 1 million of my shares today...but then i saw 20 more million sold after my sell... and none of my additional shares sold. I was thinking i was 'first' on the queue since my 1 million sold so it must have 'reached me'... but i guess not. I'm starting to think who gets to sell is just completely by random almost and not based on who is first in queue...must be cause this is on the grey sheets