This object reports the time, in hundredths of a second, since the concentrator's MAC-layer counters were last cleared, and writing zero to it clears those counters. Admins zero it out to establish a clean baseline before troubleshooting, so later counter deltas reflect only new activity. For example, an admin SETs concClearMacTime to 0 at 9:00am, then checks MAC error counters at 9:30 to see exactly thirty minutes of accumulated errors.