This is the native 64-bit counter of CLP=0 cells in the ingress direction of this channel that were tagged as low priority by the UPC policing function rather than being outright discarded. This reflects a 'tag to CLP1' policing action, meaning the source's high-priority traffic exceeded its committed rate but the network chose to downgrade priority rather than drop the cells, so admins can see partial-compliance overuse before it results in actual loss. A rising count here would prompt review of the source's traffic shaping even though no cells have yet been dropped.