The Max Guests setting sets a per-golfer limit on how many guests each person can bring.
For example, if Max Guests is set to 3, every golfer who RSVP's "Yes" can invite up to 3 guests.
Both the per-golfer Max Guests limit AND the event capacity limit apply. A guest can only be added if there is room under both limits.
If you need to change how many guests you can bring, contact the event organizer.