First some context. HiLo Lens uses optics so we can keep it small. When using HiLO Lens for normal photos it provides the same angle of view as the standard iPhone.
Instagram uses square images. So HiLO Lens offers a wider angle shot. The following images will help explain. I took the first photo with the iPhone4 camera, then cropped it to show what Instagram would upload. I took another photo with the HiLO Lens attached, from the same position, then cropped it like Instagram.