What is the correct remedy when a player draws 5 starting cards instead of 4 during initial setup (before mulligans)?

The correct remedy is to apply Rule of Drawing Extra Cards, even though the setup process is not technically a limited action. While Rule General Error could theoretically apply as a catch-all, it's not practical because you cannot rewind when the specific card drawn cannot be determined. Therefore, the closest applicable rule states: 'If the error is caught after the cards drawn are added to a private set and it is within the round cycle, the next opponent in turn order of the erroring player looks at that player's hand and chooses the appropriate number of cards to shuffle into the main deck appropriately.' In this case, the opponent looks at the erroring player's hand and removes 1 card of their choosing to shuffle back into the main deck. Note: There is some debate about whether the 'limited action' caveat in certain rule should encompass setup draws, but the practical remedy is to apply drawing extra cards since rewinding is not possible when the specific extra card cannot be determined.