Problem:

The issue here is that the customer wanted to count the number of users who have created posts under a specific post type.

Solution:

This is actually something that will require a bit of custom coding to achieve.

Here below is a small snippet that was written to help resolve this.

function count_users_with_posts() {
 
     $blogusers = get_users();
     $user_count = array();
  foreach($blogusers as $user){
    $args = array(
    'post_type'  => 'covid-19-info',
    'author'     => $user->ID,
);
$wp_posts = get_posts($args);
    if(count($wp_posts) > 0){
     array_push($user_count, $user->ID); 
    }
  }
 
     return count($user_count);
 
}
add_shortcode( 'count_users_with_posts', 'count_users_with_posts' );

Add the above to your Toolset custom code section in Toolset->Settings->Custom Code and activate it. You will need to replace "covid-19-info" with the slug of your post type that you want to count the users for.