Horizon is the maturity horizon this answer was computed under, IN DAYS — the caller's, or 120 when it stated none. Each event's as-of is its own at plus this many days, and that as-of is what decides which assertions were visible to it; an event whose as-of falls after Now is not resolved at all and is counted in Unmatured instead.
Labels is one entry per named event that BOTH matured and had at least one assertion knowable by its own as-of, in the order the events were named. The three outcomes partition the ask: len(labels) + Unmatured + Unlabelled is the number of DISTINCT events named, an event named twice having been answered once.
Unlabelled is how many matured events had no assertion knowable by their own as-of. That is the ordinary state of most traffic and it is reported rather than answered as unproductive: manufacturing negatives is how a fraud model comes to describe the incumbent block list.
Unmatured is how many named events had not aged past the horizon. They are not unlabelled — they are not yet ASKABLE, and a supervised training set must exclude them rather than treat them as negatives.
