no worries :) not sure if it's a bug but on the studio if you select the navgation and then edit the sub menu there should be a dropdown for "style" - i would figure each style would display differently but i notice no changes on my end even with dev/menu settings.... 

you can try going into Designer and then Injections and put this code in the body, save and refresh and check the result..... play with the height size number (30 imo looks nice)

<style>

  .bx-menu-main-submenu {

height: 30px;

  }

</style>