This PmTcaUnsigned64 is the highest sample-interval reading seen so far during the current Adjustment Interval, per its DESCRIPTION, and it resets to zero at the start of each new adjustment interval. This is the exact number the end-of-interval TCA logic compares against UpperBoundaryValue and LowerBoundaryValue to decide whether to fire, so watching this value climb toward (or already past) the upper boundary partway through the interval is how an operator can anticipate an Adjustment TCA before the interval even closes. For example, if UpperBoundaryValue is 600,000 and this watermark already reads 615,000 halfway through the interval, an Adjustment TCA is effectively already guaranteed at the next IntervalEndTime unless the feature is reconfigured first.