When you want to create a movie where some sets of photos are ordered and some are unordered, you can create small clusters of photos.
A "cluster" of photos is defined by the grey background behind the thumbnails of the photos. When you first upload your photos, they will all be in one large, unordered cluster. You'll see that the grey underneath all of them is the same.
By clicking and dragging a photo to the black space, off the grey, at the beginning or end of a cluster, you can create a new cluster. You can move photos from one cluster to another by dragging. Each new cluster can be ordered or unordered by clicking on the circle at the top left of a photo in that cluster. You'll notice that the numbering only changes for the photos in that cluster. When you've turned on ordering for a cluster of photos, you can drag them around so that they will be shown in the sequence that you prefer.
