To guarantee the funds are available for a transaction (A standard industry practice), a temporary authorization hold is placed on your gift card for the full amount of the order (or as much of the amount as the gift card can cover). 

 

B&N Gift Card payment authorization holds last for 24 hours, except when used to pay for pre-ordered items.  When Gift Cards are used to pay for pre-ordered items, the authorization hold remains on the funds until the item is shipped or downloaded, at which point the funds are deducted from the Gift Card.  If the order is cancelled before the item ships or is downloaded, the authorization hold is released, and the funds return to Gift Card.