This Unsigned32 (0..100) defines, as a percentage of the alert basis, the level below the basis at which a sample reading becomes a candidate to trigger an Alert TCA at the end of the alert interval, per its DESCRIPTION. Unlike the Adjustment threshold (which watches both above and below the basis) and the Overflow threshold (which watches above), this one is explicitly one-sided and below-only, which fits an Alert TCA's role of catching a statistic that has dropped rather than one that has spiked. For example, a value of 25 against an alert basis of 800 flags any sample under 600 as an alert candidate, while a sample of 950 -- well above the basis -- would never be flagged by this particular threshold no matter how high it climbs.