I ran into this issue this morning screen capturing a website for a simulation. Here are the steps to fix this issue below:
1.) Select the slide by clicking it in the Filmstrip
2.) Click on the Properties Tab and click the pencil image
3.) This will open another window. Directly below where the Gray Scale, Invert Color, and blue and golden shapes are, select crop.
4.) A crop box will then appear around your entire screen where you can edit out anything you don't want to keep in your screen capture.
5.) Click "Ok"
6.) You did it! Your screen capture is now edited. 🙂