Need to locate code to increase a top menu's character limit

I recently added a new page titled “Union Underground” under the “Features” tab on my top menu. However the text limit for a page title seems to be 13 characters so it is only displaying as “Union” in the drop down menu. I am a novice when it comes to coding and I can’t locate the place in my code to increase the character limit on my top menu drop down box. Any help would be greatly appreciated.

My blog is https://theleftahead.com