Hi there,
in your Simples CSS you have this:
.main-navigation .main-nav ul ul li a {
border-bottom: 3px solid transparent;
line-height: 1.1em;
font-weight: 500;
margin: 25px 20px;
padding-left: 10px;
padding-right: 10px;
padding-top: 5px;
padding-bottom: 5px;
font-size: 1em;
}
which also applies to the slideout nav.
So if you want to override that additional margin on the slideout menu then add this CSS:
#generate-slideout-menu.main-navigation .main-nav ul ul li a {
margin-top: 10px;
margin-bottom: 10px;
}