The purchaser will determine the number of people as they are setting up their story project. However, once your Quilted project has launched, you still add more people as long as it is before the story deadline. You can do this by sharing your unique Quilted project link and they can respond by entering their name and email address.
Login in to the video dashboard at https://app.quilted.io/signin and select "View Story" for your desired project. Then, click "Send More Invites" to access where more people can be invited by entering their email or phone number.