Play solo or team up with up to 3 friends. That is the party line in the experience description. Three is the friend group. 30 is the public server. Zombies still fill the hallways, and the description still tells you to stay quiet.
SoloPlay solo
3Friends
30Players
OffVIP servers
Solo
Play solo is the choice when you are not bringing friends. Scavenge food, store water, and barricade your apartment are still on the description, and so is the 100-day question. The public server stays at 30 players. Playing alone does not open a private building.
The room
Other survivors can already be in that 30-player server. Play solo means you did not bring the friends the description allows. It does not clear the room, and it does not raise the friend group past three.
Cooperative
Team up is the other choice in the same line, and it stops at up to 3 friends. Those three are the friends you play with. People outside that group can still be on the server, because the catalog maximum is a separate 30.
Two caps
Keep the numbers apart. Up to 3 friends is the group named in the description. 30 players is the public server. A full group of three still shares that server with whoever else joined.
Server size
Use the friend line when you are inviting. Use 30 players when you want to know who else can be in the building. Someone who came alone and someone who brought three friends are under the same server cap.
Fact
Figure
Friends
up to 3 friends
Solo
Play solo
Server
30 players
VIP servers
Not allowed
Join price
None listed
VIP servers are not allowed, so the catalog has no private server that would change either number. Joining lists no Robux price. The pinned hallway is the corridor in front of you either way: one survivor against the wall while zombies approach.
The shared hallway: one survivor against the wall while zombies approach, whether you came alone or with the three friends the description allows.