What kind of contest is it? Is it a contest where players are competing each other by making deposit as much as possible during the promo period? If it works like this, so how can even players know how much is the deposit amount from other players? Do you have a public leaderboard for this or you will only announce it later once the contest is done? If there is no way to check/verify other player's statistic (the deposit amount), I think it is not a fair contest because you can take any username and announce it as the winner.