Both amounts seem low. The before taxes payout is usually about half of the face amount. It’s based on present future value.
GA has a state income tax I believe. In that case $173 million might be close. If I won it in TN (I don’t waste money on the lottery) my after taxes one time cash would be closer to $195 million.
The Georgia half would be likely less than $120 million AFTER taxes. The feds only withhold 25% and winner will likely owe 39% or so.
http://www.usamega.com/mega-millions-jackpot.asp?d=12/17/2013