Every progressive is funded by a small slice of each qualifying stake, set in the game rules. When the jackpot is won, it drops back to a seed amount paid by the operator or the game maker, and the climb starts again. The slice set aside for the pot comes out of what the game would otherwise pay in regular wins, so the everyday prizes on a jackpot slot tend to be smaller than on a similar game without one.
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 own rules.
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 feed it.