Sometimes the payout shown includes the money you wagered for instance, if you bet $10 to win $50, the payout would show $60. If it doesn't, just add the amount you bet to the potential winnings to determine the total payout. You can also calculate potential odds and payouts before making a bet.
In order to understand whether a bookmaker is safe or not, you first need to look at the bookmaker's license. In the case of Sportingbet, the bookmaker has several licenses. This means that Sportingbet is recognized as a secure and legitimate company.