To change the max number for the "Total Guests" drop-down list on the RSVP page you need to go to the "Menu - Event Settings" dialog, tab "RSVP" and enter new value in the "Maximum number of people allowed for each guest" input.
The default value 4 means that a guest can bring 3 people along with him. When you set it to 1 it means that the guest can come only alone and the "Total Guests" drop-down list on the RSVP page will be hidden.