By selecting a Category checkbox, you are stating "I would like to see all packages in
this category." Only the packages in the selected categories will be displayed. So
similarly, by selecting all the Category checkboxes, you are stating "I would like to see
all packages in any category." But some packages in the gallery do not belong to any of
the categories listed, so they will not appear in the results. To see all packages in the
gallery, uncheck all the Categories, or select the packages tab again.