Zero, missing, and outside coverage
Three different answers
Zero means the source reports the measurement and its value is zero. Missing means the measurement is absent. Not applicable means the statistic does not describe that opportunity, such as exit velocity on a pitch that was not hit. These answers must never be exchanged.
Why old records need extra context
Historical box scores and play-by-play have different levels of completeness. A game may have a final score while lacking pitch sequences, runner movements, or a complete individual pitching line. A pitch-based record therefore cannot automatically inherit the coverage of the final-score database.
A cutoff is not a most-recent claim
A closed window such as 1897–2019 ends in 2019. Its last occurrence is the last found inside that window, even if similar events happened later. The ejection-log lists retain a closed window rather than claiming to be updated with today’s games.
How to verify a claim
Open the definition, inspect the occurrence list, and follow the game evidence. Check whether regular season, postseason, extra innings, and shortened games are included. When a source is incomplete, describe the result as a recorded count or documented minimum instead of an all-time certainty.
Further reading: StatGami methodology, source coverage and terms, Retrosheet field definitions, and nflverse update schedule.