Having multiple numbers is possible and one of the best reasons to use Burner. Simply open Burner and tap “Create Burner” on the bottom of the app’s page.
Then, depending on your credits, you may select one of the four types of Burners. As long as you have enough credits, you can as many additional Burner numbers as you'd like.
And if you need more credits to buy or extend your burner, just tap “Get More Credits” at the bottom of the screen!