The Enter Details page allows you to set the Total Invited number as the default for each guest invited to your event. You can find this feature by toggling the "Allow guests to bring additional guests" option in your Event Page Settings on the Enter Details page. You should set this number as the number that applies to the majority of your guests (e.g. if most are couples, set this as 2 and manually change the other guests to other numbers).
You'll be able to change this per email address on the Add Guests page.