Is the 40 card deck size a minimum or an exact requirement in Riftbound?

Ruling: In casual OPL play, your deck must be at least 40 cards (minimum). In high OPL tournaments, your deck must be exactly 40 cards. The 40 cards consist of 39 main deck cards plus 1 chosen champion.

Nuances:

• Legends, runes, and battlefields do not count toward the 40 card deck size
• In BO3 matches, you can change your chosen champion in games 2 and 3 to another champion from your deck or sideboard, but game 1 must use the chosen champion listed during deck registration