Customs exemption caps duty on specified Chapter 8 and 9 goods to a fixed ad valorem rate on import. Central Government exempts specified goods under listed sub heading numbers of Chapters 8 and 9 from so much of the customs duty leviable under the First Schedule as is in excess of the amount calculated at the stated ad valorem rate when imported into India, thereby capping the effective duty payable for those enumerated tariff sub headings.