The classification of images into stellar, non-stellar is an automated process. There are some important limitations of this procedure. When the lowest measured isophote of two or more images touch the images get treated as a single 'merged' image. Merged objects are plotted as single open ellipses. The size of the ellipse is proportional to the isophotal size at the lowest measured isophote.
Many cases are easy to interpret particularly stellar classified elliptical objects.
On very rare ocassions objects are 'missed' by the APM since the background following algorithm uses a fixed scale size in order to track the diffuse halos that appear around bright stars or large galaxies. In addition large complex objects such as bright galaxies, scratches and diffraction spikes of bright stars may be 'broken up' into a swarm of many smaller images. These cases are usually obvious.