Aperture 3: Number of Aperture items seem to vary when sharing with the Media Browser

Previews from your Aperture library can be shared with other applications, like iMovie, Pages and GarageBand by using the Media Browser. Sometimes, the number of items displayed in your Aperture library may be different than the number shown in other applications. There also may be some differences in item count between some of the other applications. This article explains how items are counted.