Portfolio Excerpt

Hello,
I’m trying to add portfolio items and would like for them to display excerpts on the Portfolio archive page. I understand that the standard portfolio layout should do this for me. My problem is that on my New Portfolio Item page, I don’t see anywhere an option to add the excerpt. When I click on Screen Options, there is no option to view Excerpt, see screenshot. Not sure if there is a settings issue somewhere that is causing it not to show up?