>>29902031When you first encounter a Pokémon, only the first slow matters. When a Pokémon tries to call for help, it'll call one from the same position, but on a random slot.
So if you find a Pichu from Route 1/Table 2, when it calls for help it'll either call another Pichu, a Pikachu or a Happiny.
This is just what I read from another thread so I'm not sure on the exact details.