XF 2.1 findThreadsWithLatestPosts

[Robert9]

Where in this code is the trigger to fetch the last post, please?
I need the first post and i dont see the point to change that.

class Thread extends Repository
{
    public function findThreadsWithLatestPosts($readMarkingCutOff)
    {
        return $this->finder('XF:Thread')
            ->forFullView(true)
            ->with('Forum.Node.Permissions|' . \XF::visitor()->permission_combination_id)
            ->where('discussion_state', 'visible')
            ->where('discussion_type', '<>', 'redirect')
            ->where('last_post_date', '>', \XF::$time - $readMarkingCutOff * 86400)
            ->order('last_post_date', 'DESC')
            ->indexHint('FORCE', 'last_post_date');
    }
}