Historical Rules · 25 January 2019
Rule 208.2b
Official source text from the 25 January 2019 Rules release
The card may have a static ability that creates a replacement effect that sets the creature's power and toughness to one of a number of specific values as it enters the battlefield or is turned face up. (See rule 614, "Replacement Effects.") Such an ability is worded "As [this creature] enters the battlefield . . . ," "As [this creature] is turned face up . . . ," or "[This creature] enters the battlefield as . . ." and lists two or more specific power and toughness values (and may also list additional characteristics). The characteristics chosen or determined with these effects affect the creature's copiable values. (See rule 706.2.) While the card isn't on the battlefield, its power and toughness are each considered to be 0.