Five Below authorizes your card when you place an order, then officially "bills" you when your order ships (just like most other retailers)!
Your card will be authorized for the total amount of the order, however, the card will not be officially billed until the order ships (when you receive tracking). Only one completed charge (per order) will be on your account :)
ps: if you're seeing a different amount charged to your card once your order ships, an item may have gone out of stock and you were not charged for it. this will be reflected in your shipping confirmation at the bottom of the email!