Central Excise tariff amendments require computing exemptions as a percentage of aggregate customs duties and clarify exemption scope. Amendments revise exemption calculation language to require computing a specified percentage of the aggregate of the duties of customs, insert illustrative stepwise computations of basic, additional and special additional duties to demonstrate resultant excise liability, update tariff table entries by adding, substituting or omitting specific items (including waste and scrap entries and nylon tyre yarn), substitute cross-references to the CENVAT Credit Rules, 2002, and tighten exemption conditions and provisos that limit applicability and clarify scope of nil-rate clearances.