At 14:14 you select all the circles that are part of the cloud and delete the faces. I am not on the same page as you at that moment because all my circles are separate objects and they need to be one object. How do I do that?
Keep in mind that Kent duplicated the circles inside edit mode, which makes them part of the same mesh object, they remain contained as part of the same mesh when you do it in edit mode. You probably at some point went into object mode as you duplicated them and that made them each one their own object.
