When Sirius XM says they are offering stock at a "fixed" price of $1.50 per share, what does that mean?

I was reading some finance news stories and it said Sirius XM (the new merged company) is offering a lot of shares at a fixed price of $1.50. When I checked the stock it said it was trading at $1.58 at the end of today. Does that mean that they already sold all the shares that were at the fixed price of $1.50 and the stock went up since, or is it still possible for buy shares at the fixed rate?