Multi-line site-description

Hello again, my question: is there any way to add another line of text after the site description on the main page’s header? I tried to add a line break directly to the customizer but it didn’t work. I searched the header php for my site description but couldn’t locate it anywhere. As of now it reads:

Fostering tangible hope for a purposeful future

I would like to display this:

Fostering tangible hope for a purposeful Future
10 year milestone (2005-2015)

The site is http://www.ai.dorianlatelle.com

Any help would be appreciated, thanks!