Please add the following code in your active theme's functions.php file.  Please change the red marked code before using, set it the current post ID. 

// disable notifications from the specific (X) post
add_filter('wpdiscuz_email_notification', function ($val, $emailData, $comment) {
   if ($comment->comment_post_ID == X) {
       $val = false;
   }
   return $val;
}, 1, 3);

//  followers
add_filter('wpdiscuz_follow_email_notification', function ($val, $followerData, $comment) {
   if ($comment->comment_post_ID == X) {
       $val = false;
   }
   return $val;
}, 1, 3);

I'm sorry, but there is no option for this. You should do it using wpdiscuz_email_notification hook.  I mean that disable the subscription for the current post using the hook.