This is a good catch. I have added it to the task list and will do once I will start to work on next update. Meantime follow the steps to fix it.
The most simple solution is to add text-align: center to the wrapper as below
Find css rule .qam-main-nav-wrapper in qa-styles.css and add text-align: center;
If you apply outside the media query than it will apply to all by default and things will be aligned for the desktop too. So if you want it only for specific screen than find the appropriate media query in css (it should be near around it) and add text-align property to only that screen size.