Partial exemption of auxiliary duty on goods already relieved from basic customs duty prevents excess ancillary levies. Exempts from levy any portion of the auxiliary customs duty in excess of a 25 per cent ad valorem rate on goods that are partially or wholly relieved from basic customs duty by the notifications listed in the Schedule; the exemption is exercised under statutory taxation powers and is subject to the conditions, if any, attaching to those original notifications, with valuation determined under the customs valuation provisions.