Pokémon Pokopia’s 300 featured Pokémon come from Generations I through IX.
That range covers nine Pokémon generations. The game therefore draws on characters introduced across the franchise’s history, from the original Kanto-era roster through the Pokémon introduced in Generation IX.
The generational range is different from the game’s story setting. Pokopia takes place in a post-apocalyptic version of Kanto, but its playable world is populated by a selection of Pokémon from many generations rather than only by the original Kanto species.
The figure nine also should not be confused with the game’s 300-Pokémon roster. Nine is the number of generations represented; 300 is the number of Pokémon selected. These are related facts, but they answer different questions about the game’s scope.