[USR-TC] TRAP: Card inserted into slot 30?

Today I got strange trap on alarm server: Card inserted into slot 30. How is it possible? I know that this chassis has only 17 slots. There are variable values of this trap: ... .iso.org.dod.internet.snmpV2.snmpModules.snmpMIB.snmpMIBObjects.snmpTrap.snmpTrapOID.0 enterprises.usr.0.1 enterprises.usr.nas.nmc.nmcTrap.nmcTrapSequenceNumber.0 288 enterprises.usr.nas.nmc.nmcStat.nmcStatEventId.0 288 enterprises.usr.nas.nmc.nmcCfg.nmcGmtime.0 1044710490 enterprises.usr.nas.chs.uchasSlot.uchasSlotTable.uchasSlotEntry.uchasSlotIndex.1 30 enterprises.usr.nas.chs.uchasSlot.uchasSlotTable.uchasSlotEntry.uchasSlotModuleType.1 enterprises.usr.nas.chs.uchasKnownTypes.uchasKnownModules.uchasSlotUnknown ...