Is it free if we loss? Or you will give refund for the first bet if we loss? or something else.
It is not a free bet, but actually a money back guarantee. You have to place a real bet on a horse to win a race. If your horse wins, you get nothing. If it losses, your money is returned back to you and you can use it to make another bet. 5 mBTC is the max that you can bet with for this promotion. There are probably many more things you need to pay attention to so read the rules carefully.
So what is the benefit of this free bet in case of a win ? Your money will be returned if you lose the bet and you have the original money with you in case of a win. So in theory, the win or loss does not matter in the risk free first bet as you gain nothing from that bet and maybe it is helpful for the people who are new to the betting.
The point of the promotion is to have a fee swing. If you win you win, if not you get a second chance at winning. If you have never tried betting on horse, it gives you the opportunity to do it with less risk. Nothing is more exciting than betting on horse racing.
Have you ever seen a reaction like this from TV presenters like this for any other sport?
https://www.youtube.com/watch?v=Xs1X0ptj_z4