Site Administrators can increase or decrease the child profile limit through your Site Settings. Your monthly invoice is based on your child profile limit, not the number of active children on your site, so be sure to keep this up to date.
You can change the limit, in increments of five, using the arrows below. Once you're happy with your new limit simply click Save and confirm the change.
Once saved, you'll see the profile capacity limit on the Billing page will have updated. The change will be reflected on your next invoice.