how to change video size in project pane? (iMovie 10.0.8)

I cannot figure it out, but when it's larger it's easier to work on...

See my two enclosed screen shots, you can see that the video in the on project pane is significantly bigger but I don't know how I got it like that.... All video is from the same camera, same resolution, same everything, even the same day.....

In this one it's big

In this one it's small

How do I get it BIG?