Add title attribute only in one menu

Hi,

I managed to show the title attribute in the menu using this topic
http://wordpress.org/support/topic/display-title-attribute-in-menu?replies=3

I have at least two different menu’s, but I can’t seem to find out how I just add this title attribute to the main menu by changing some php codes.
The top menu changes when I change the style of the attribute, which is logical.
Could someone tell me how to change the php code so the attribute will only apply to the main menu?
Website I am working on: http://www.vakantiewaddenzee.nl/vakantie/

Thanks in Advance.

Dieuw

p.s. the solution in this topic doesn’t work on my site: http://wordpress.org/support/topic/how-to-show-the-description-of-the-menu?replies=9