Assuming you've passed this stage, the slot machine will continue to grant users 15 special rounds and add the x3 multiplier to all your wins. It seems that these waves cannot be reactivated, so it is best to take advantage of them if given the opportunity.
What makes this level even more satisfying is that it can be activated in "Dragon Features", which actually makes the title come true and doubles your destiny. We don't usually say that slot machines do just that. These are just two icons in the odds table, which means that when you play with real cash, you have more things, such as searching for five crane cards.