WordPress at a glance
filter is not described

wp_count_posts filter-hook . WP 3.7.0

Modify returned post counts by status for the current post type.

Usage

add_filter( 'wp_count_posts', 'filter_function_name_5110', 10, 3 );
function filter_function_name_5110( $counts, $type, $perm ){
	// filter...

	return $counts;
}
$counts(object)
An object containing the current post_type's post counts by status.
$type(string)
Post type.
$perm(string)
The permission to determine if the posts are 'readable' by the current user.

Where the hook is called

wp_count_posts()
wp-includes/post.php 2424
return apply_filters( 'wp_count_posts', $counts, $type, $perm );
wp-includes/post.php 2389
return apply_filters( 'wp_count_posts', $counts, $type, $perm );

Where the hook is used (in WP core)

Does not used.