in components\com_k2\models\itemlist.php
search this:
$categories = K2ModelItemlist::getCategoryChilds($id);
and remplace for:
$categories = K2ModelItemlist::getCategoryChilds($id,true);
in the function "countCategoryItems"
in components\com_k2\models\itemlist.php
search this:
$categories = K2ModelItemlist::getCategoryChilds($id);
and remplace for:
$categories = K2ModelItemlist::getCategoryChilds($id,true);
in the function "countCategoryItems"