On the left, in the image below, is a default view of an entry publish page when 3 category groups are assigned to the channel, and on the right are 2 Advanced Category fields assigned to the channel. They look very similar, and that is by design, however, they behave differently. The "Call Signs" field on the right has been configured to require at least 1 category selection, but no more than 3. It also happens to be listing the same categories from the Call Signs category group on the left. The rules, and each of the category options were selected to display in the "Call Signs" field settings page. If the default category group remains visible on the publish page users can still interact with it, but if any category in the default category group is assigned as an option in an Advanced Categories field, then the categories selected in the Advanced Categories field will superceed anything selected in the default category group.