So I made a little progress,
when I add, in hor_cats show_count=1& like this :
$list_cat_string = wp_list_categories('show_count=1&orderby=' . $sort_order . '&order=' . $order . '&title_li=&depth=' . $levels . '&exclude=' . trim(str_replace(" ", "", $exclude)) . '&echo=');
it displays the number I want but under the category box, I don't know why, like you can see currently on my website : http://www.radiatorhymn.com
The problem is, I have no control at all, on how to display it just after the category name.
I don't understand which function call this list_cat_sting var, to display the informations it gets.
I saw the hor_cats function is called by bfa_header_config, but after some test no results.
I finally thought I should add a line in hor_cats like a pregreplace, to add the value at the end, but I really don't understand how it works.
It's very boring to be so closed of the goal and can pass through it, it's probably very simple.
I just want to solve this to publish my website.