Provides a number that lets a network engineer implement statistical multiplexing when admitting Frame Relay calls under overload conditions, with the exact value depending on factors like expected sustained SVC call setup and clear rates and how conservatively the engineer wants to handle simultaneous mass-clear error conditions. The description points admins to the vendor's Engineering Guidelines for setting this appropriately rather than choosing an arbitrary value. An engineer tuning a Link Processor expecting bursty SVC setup and teardown activity would set this headroom value per those guidelines to avoid over- or under-admitting calls during a burst.