What matters first in "must drop jackpot" is where the prize money is drawn from. A jackpot is the largest prize a slot can pay, and the way it is funded decides how large it can grow and how it is won. Fixed jackpots are set amounts written into the paytable. Progressive jackpots rise with every stake placed on the games linked to them until someone wins, then reset to a starting figure. Knowing which kind is on the screen explains the number shown above the reels.
Jackpots are won in one of two ways. Some need a specific combination, such as five jackpot symbols on a line at the maximum stake. Others are triggered at random after any spin, often through a jackpot wheel or a bonus game that picks one of several tiers. Random triggers usually give a larger stake a better chance of starting the jackpot game, a rule the game information states plainly in most titles.
Progressive jackpots differ by how widely they are shared. A standalone progressive grows from the stakes on a single game, a local one is shared by several games in one casino, and a network jackpot collects from the same games across many casinos at once. The wider the pool, the larger and rarer the top prize. The jackpot display usually names its type, and the game rules say which casinos or titles pay into it.
Some progressives carry a must drop figure, a ceiling by which the jackpot is guaranteed to be won, which makes a pot close to its limit more likely to pay soon. Very large wins are often paid in instalments or after extra identity checks, and the terms say how. A jackpot that has not dropped for a long time is no more due than any other, unless a must drop ceiling is written into its rules.
Not always: some tiers require a minimum stake or an optional side bet, and play below that level still feeds the pot while the grand stays out of reach.
The game rules list the titles and casinos contributing to a network pot; the wider that pool, the larger and rarer its top prize tends to be.
A small slice of every qualifying stake, fixed in the game rules, feeds the pot, and that slice lowers what the regular wins on the game can pay.
A progressive with a ceiling by which it is guaranteed to pay, so a pot near its limit is likelier to drop soon; without such a ceiling no pot is ever due.
Mini and minor tiers drop far more often than major and grand, and the grand tier is the rarest because it holds the largest prize in the game.
Some pots need a set combination, such as five jackpot symbols on a line at maximum stake; others start at random after any spin, often through a jackpot wheel.