How can I edit the shortcode to show 2 months at a time on our site?

Hi! As we are nearing the end of July and would like to start accepting appointments for August as well, I'm wondering if there is a way I can edit the shortcode [app_monthly_schedule] so that both the months of July and August will be displayed on this page: http://road2argentina.com/interview-scheduling/. I already tried adding add="1" to the shortcode, but that displayed only August, not July and August. Hope someone can help clear this up for us. Thank you!