Change length of sub menu descriptions field

Hey guys,

So I’ve created a few sub menus, but they are capped off even if there’s enough space left.

Let me illustrate:

How To Choose Your Headphones
Lesson 1 – Open-Back
VS Closed-Back
Headphones

Naturally I want it to be:
How To Choose Your Headphones
Lesson 1 – Open-Back VS Closed-Back Headphones

Please have a look at my site and just hover on the first menu.

Any help will be appreciated!