If you go to a game page and tap Edit you can change a game’s properties.
These properties are: Player count, Play time, Minimum age and Base/Expansion/Both.
When you add a game without a BGG link, you can set these properties when adding, but you can always edit them later.
When you have a game with a BGG link, you can also edit these properties, to suit your preferences better.
👉 Why would you want to change these properties? Because you can use them in the Custom Filter to search for games.