This is the internal numeric object identifier UCS Manager assigns to the external destination binding attached to a scheduled backup/export policy for its own database bookkeeping. Admins never set this value themselves; it exists so UCS Manager and its internal fault/event/audit-log records can cross-reference this exact BackupExportExtPolicy instance even after its human-readable name or DN path changes. You would typically see it as an opaque string like 138543 rather than anything that maps to a hostname, schedule, or file path.