You can see your staking options and choose your preferred level on the betslip of the relevant pool. As you change your stake per line, the jackpot prize you are playing for changes in proportion to your stake, as shown in the pool header.
For Win pools, the maximum (full unit) stake per line, which plays for the full jackpot, is £2 (or currency equivalent). There are then three fractional staking options: £1, 50p and 20p (or currency equivalent).
For Finishing Order and Place pools, the maximum (full unit) stake per line, which plays for the full jackpot, is £1 (or currency equivalent). There are then three fractional staking options: 50p, 20p and 10p (or currency equivalent).