You are probably best to ring the hotline. It's mentioned a lot in these threads or use Mr Google.
My understanding is that everyone who accepted off market gets the higher offer regardless of when they accepted so if you accept the offer you get 4.6c and a cheque in the post. If you sell in market you get whatever you sell for.
Hancock said that if they got 90% they would compulsory acquire the rest and delist Atlas. I believe they will get 90% now FMG have sold. I also believe they will extend the offer by at least 2 weeks.
However DYOR.
AGO Price at posting:
4.3¢ Sentiment: Sell Disclosure: Not Held