Make mobile dropdown menu display on the right

Hi there

Thanks to your fantastic support (https://generatepress.com/forums/topic/align-hamburger-with-secondary-menu-on-mobile/) I was able to get just the right layout of the header elements on mobile.

But (sorry!), when you click the hamburger on mobile the dropdown menu appears on the left, instead of below the hamburger on the right. It's a little hard to see because it works correctly in the customizer mobile view but not on an actual phone (I guess due to the narrower screen?). There's a screenshot of my phone here: https://www.dropbox.com/s/qsye7dfxlgdr0tg/Screenshot_20200405_102009_com.android.chrome.jpg?dl=0

How can I get that dropdown to sit on the right instead of on the left?

Thanks
Lucy