Rarity is history, not a forecast
What the number answers
An observed frequency answers how often a precisely defined event appears in a precisely defined collection. If a record occurs 100 times in 100,000 eligible games, that is one recorded occurrence per 1,000 games. It does not say that the next game has a one-in-1,000 chance.
Choose the right opportunity
A game contributes two team-games. A single game may contain several player achievements, several innings, and hundreds of pitches. A rate per game cannot be compared directly with a rate per pitch or per player-game. Read the unit beside the number before comparing two records.
Why the next game differs
The players, park, opponent, weather, rules, and era change the conditions. Events within one game are also related. Repeatedly multiplying historical frequencies as if they were independent can produce impressive-looking but unjustified odds.
What the rarity score means
The board’s 0–100 score helps order notable events. It combines measured rarity with presentation rules. A score of 90 means a high position on that scale; it does not mean a 90% probability, confidence level, or percentile of players.
A useful way to quote a record
State the definition, count, opportunity unit, coverage dates, and latest verified game. Link the occurrence list. For example: “The covered records contain N qualifying games from YEAR through DATE.” That sentence remains useful without pretending to predict the next result.
Further reading: StatGami methodology, source coverage and terms, Retrosheet field definitions, and nflverse update schedule.