This Unsigned32 is a lifetime count of samples that were collected but not actually used by the Adjustment TCA feature for this PM instance, per its DESCRIPTION. A sample typically gets discarded rather than processed because of a discontinuity in the underlying data -- a counter wraparound, a bin marked invalid, or a state change mid-sample -- so a rising discard count is a sign of instability in the underlying PM data collection itself, not of the traffic or errors being monitored. For example, a sudden run of discarded samples that lines up with a logged card reboot is expected and benign, but the same run of discards with no corresponding reboot event in the logs is worth escalating as a possible PM subsystem problem.