If a user who has already won a prize is picked, calculations are done again and a new user is picked.
Ah thanks, funny I've been on this site for such a long time and I never actually really wondered. Won the lottery once, was not a bad win but always hoping to hit the big one at #1, even if it's this week's prize which isn't so big I'll be really happy! almost 0.5% of total tickets (my autobet keeps dying recently). But already making a new personal record for golden tickets so fingers crossed;)