Set Unity Network Match as private in game

Hello! I'm making an online game with the deprecated Unity Network and I use the matchmaking system.
How I can "hide" a match when for exemple : To start the game we need 2 players minimum.
I create a match with 4 players slots but server player want to play with 2 players, so he will start the party.
After the beginning of the party, I want to remove the match from the matchmaking list to avoid new player.
Thanks a lot!