The menu is working as it was intended.

When viewing a section, the menu item for that section will be underlined.

So the first section you have on your website is the Blog section with the latest posts.

Which is why the “News by Stama” menu item is underlined, because that is the first section on the home page.

If you view the demo for the theme you will see how it works.

If you don’t want this you can use a bit of CSS code to hide it.

Use the following code in the Custom CSS field of the Custom Code section in Integral Options,

.navbar-default li a:hover, .navbar-default .navbar-nav > li.active a, .navbar-default .navbar-nav > li > a:hover {
border-color: #fff;