Fulton Template - Decrease width of Pop Up Menu from Hamburger?

Site URL: https://broccoli-flugelhorn-6ey6.squarespace.com/

Hi everyone,

I just wondered if someone would be able to help please! I am half way through building a site in Fulton as I love the hamburger menu icon. However, I am trying to figure out how to reduce the width of the page that pops up with the menu on - see below; so that it is a third of the page, rather than the whole page. Is that possible?? 

Thank you to anyone in advance that can show me the way!

Password to view site is: broccoli

iT already 80% of the page do you want it smaller?

Yes please! I'd like to make it about 30% of the full page if possible? Thanks so much for replying!

21 minutes ago, viccismarshall said:

Yes please! I'd like to make it about 30% of the full page if possible? Thanks so much for replying!

#overlayNav {
  width: 30%;
}
@media only screen and (max-width: 600px) {
    #overlayNav {
      width: 50%;
    }
}

Thank you thank you thank you!

Works perfectly.