Multi-level progressives have multiple levels of jackpots. This means that the jackpots with the best odds of winning are the ones that are getting closer to the upper jackpot value.
A mystery progressive payout could hit at any time within the specified range. This means, for example, that the jackpot meter will say that it will pay out before it reaches $1,000, but at a randomly generated number less than the declared value. Mystery progressives do not require a winning combination, and are instead guaranteed to randomly hit within a specified range.
Mystery progressive jackpots are different from standard jackpots on slot machines in that you can better predict when they’ll hit.