You can set your subpages on your vertical menu to open to the right or to the left. This is a useful feature and the preference usually depends on the position of your menu on your page.
To change the direction of the subpages in a vertical menu:
Click your menu.
Click the Layouts icon.
Select an option under How do submenus open?:
To the right: The subpages of your submenu open to the right of the menu item.
To the left: The subpages of your submenu open to the left of the menu item.