Partial exemption from auxiliary customs duty where goods are partly or wholly exempt from basic customs duty, subject to valuation and conditions. Partial exemption is authorised for the auxiliary duty of customs on goods partially or wholly exempt from basic customs duty, relieving that portion of auxiliary duty which exceeds an amount computed at a fixed ad valorem rate of the goods' value as determined under customs valuation. The exemption applies only to goods covered by specified prior notifications and remains subject to any conditions attached to those notifications.