There's a guaranteed $2 million roll increase per draw, although usually the amount is much higher.
The estimate takes into account how much money has already been accumulated since it was last won, and how much more is expected to be added for the next draw based on ticket sales. The advertised current jackpot amount is an estimated value prior to a draw. Check the Mega Millions Jackpot Analysis to find out how much you would end up taking home after tax, based on the state where you purchased your ticket. You can see the annuity value and the cash value of the grand prize.
