This value holds the Q.931/Q.93b failure cause code recorded in the cause information element for this specific failed call, per the description, using the same code set as svcAtmConfigQ93bLastCauseTx/Rx (e.g. unallocated number, no route to destination, user busy). Unlike those two port-wide 'last cause' scalars, this value is preserved per logged failure, so it lets an admin build a real distribution of failure reasons over many calls on this port instead of only seeing the single most recent one. Seeing a cluster of entries with vcc-unacceptable-30 (10) would point at incompatible traffic/QoS parameters being requested repeatedly, not a one-off glitch.