That's how nested projects work.

Instead of opening up the project directly (File > Open Project) you told PD19 to insert an existing project onto your timeline as a nested project, which it treats as a single clip on the main timeline.

To see the full contents of the project, you have to double click on it to drop down one level. There's nothing stopping you from continuing like this and producing the nested project as your finished video, but if you abandon this and simply open the original project you'll be on more familiar ground.

The PD19 Help file is a good place to learn about these new features.