If you're seeing double-charges or overcharges for one booking, don't worry! This is completely normal, as airlines will place an authorization for the purchase to ensure that there are ample funds in the account before processing the payment. Once the official purchase is processed, the authorization will drop off within a few business days, leaving just the one official charge.
Keep in mind that if you’re booking for multiple passengers, the airline may place individual charges for each ticket issued, and you might see multiple charges of the same amount that add up to the total cost of the trip.