yes, this is a good question. 
You can only withdraw what is left, so if you lose all, there'll be nothing to withdraw. The good news is, if you win you will be able to withdraw your profits as well. Pretty fair and square, isn't it?
After registration, I receive an email with this:
"Start playing with up to $1,500 in bonuses and 100 Free Spins. To activate your bonus, simply make a deposit and the bonus will be automatically applied."
So, maybe we're talking about these 100 free spins, though I don't see it as an option how to claim it, except to use "Bonus Code"
Also in the same email is "Learn more about our Welcome Package here" but it's not linked to anywhere, just a text.