Yes. Credits can be used to book a reservation past the expiration date as long as the reservation is made BEFORE the credit expires.
Ex. A credit that expires on June 25, can be used on June 24 to reserve a class on June 30. If the customer cancels the booking after June 25, they do not receive the credit back.
These credits CANNOT be "grace cancelled" or "grace no-showed." If a late cancellation or no-show happens using this credit, the credit will be removed.