Snapshot labels are added differently to objects, depending on the object type.
For structured documents, snapshot labels are added to elements. If you are adding a snapshot label to a structured file, the label will actually be added to the root element of the object, not the file name. If you are adding a snapshot label to an element within a structured file, you must expand the hierarchy of the file in the Navigation view to drill down to and select the element of interest.
For example, you can add a snapshot label to just a single step element in a DITA task topic. Or you can add a snapshot label to a single topicref element in a DITA map, or to a group of topicrefs within a topicgroup element.
For unstructured files, the snapshot label is added to the file name.