One entry per event (a regatta, or the club's own season). The prefix scopes the series and race IDs, so two events at this club can each hold a "Race 1" on the same date without colliding — leave it blank to derive one from the first URL. Changing a prefix after races are imported creates new IDs.

Races are only fetched from SailSys for what is listed here. A series imports one specific series, including past seasons. A club imports whatever series that SailSys club currently lists, so new seasons appear on their own — but it never reaches past seasons, which is what series entries are for.