When you find all 10-20, you know that you found all the Pokémon available in that route and can move on. There are a TOTAL OF 10-20 Pokémon that can spawn in every route (depending on the area of the route). If this were not done, then you would probably only ever see 2-3 Legendary Pokémon in the ENTIRE game. This had to be done to maximize all Legendary Pokémon being available to spawn in the game (out of the 500+ regular Pokémon). Many Legendary Pokémon are available to spawn so you may notice a high abundance.
DetailsThis mod randomizes the following aspects of the game:
Personally, I don't play Pokémon so I had to do A LOT of research before proceeding with this task of creating a randomizer. There is a lot of valuable information here.
Please read everything to understand how it works and how to get the proper files for your game.