After your session, you'll receive a link to all of the proofs.  From these images, you'll select the number allotted in your package.  If you want to order more at that time, you can.  However, you may know in advance that you'd like two different shots of each child, one of the whole group, and one of you and your partner... yet your package only allows for 3 images.  You can then choose this add-on to ensure that even with a shorter session, we'll get enough varied images for you to choose as many as you'd like!