A starting Fargo can be any number. It originates with the person who first enters the player as a new player in the system. Usually a league operator who has access to LMS. Or maybe a tournament director in another setting.
Here in our league we task the team captains to give us an accurate starting rating guesstimate for their new players based on their assessment of play compared to our established players. I always go with that unless I know better. It only matters the first little bit after which the player will level off where they belong regardless of where they started.
What we do works well for our league.
JC