I think it works like this, let's say there is a real vs barça match and ps3838 for example has odds @1.8 for barça to win while dafabet on the other hand the next have odds at @1.3 for real to win. Here we see that if barça wins your total return on both bets will be 50 euros. That is to say 80-30, on the other hand if the real wins or draws your money 100 euros is refunded. And I believe that here it is clear that being refunded is better than losing.