Exemption from excise duty: specified goods allowed duty ceiling with option-based rate and cenvat credit implications. The Government, exercising powers under section 5A of the Central Excise Act, exempts the excisable goods listed in the Table from so much of the excise duty as is in excess of the amount calculated at the notified ad valorem rate, by reference to specified First Schedule tariff chapters, headings, sub headings or tariff items and corresponding product descriptions; the notification includes explanatory definitions for certain entries and records multiple subsequent substitutions, insertions and omissions which modify the scope of specific Table entries.