When a Syndicate wins a jackpot, the prize is split among all Syndicate contributors in proportion to the % of the ticket they own. For example, if the total cost of a Syndicate ticket is £100 and you have contributed £10, you own 10% of that ticket. And if it goes on to win £1000, you will receive £100.
You can see the total payout of a Syndicate you’ve contributed to, as well as your own payout, by navigating to the relevant ticket under “My tickets”.