Each individual Jackpot fills up with a percentage of all the bets placed on that specific game mode.
Each roll of the Wheel/Roulette/Crash has a fixed chance of triggering the Jackpot. If the Jackpot triggers, it gets split between all eligible users in that round.
Eligible users are players who bet on the corresponding jackpot color for Wheel of Fortune, all the players in that round for Roulette and all the players that made profit in that round for Crash.
Please click on the Info button next to the jackpot to read the full description for that gamemode.