This Gauge32 gives the finalized count of cells received with HEC or encryption errors during the previous 15-minute period. Because it's a completed sample, an admin can use a run of stuStatsPrevAtmHec readings to determine whether HEC-related issues on this STU are chronic or were limited to a single period. For example, a sudden one-time spike in stuStatsPrevAtmHec followed by a return to zero in later periods would suggest a transient event like a single key-renewal glitch rather than an ongoing hardware fault.