Hey guys somehow this helped me to get count of NAND operation.
Because I dont need ti iterate through those posts, I used `found_posts` of `WP_Query` . Subtracting my posts count from total post count.

I'm still waiting for a better way if any. Thanx [Luis][1].

    $myargs=array(
    'posts_per_page' => -1,
    'tax_query' => array(
            'relation' => 'AND',
            array(
                'taxonomy' => 'author',
                'field'    => 'slug',
                'terms'    =>  $author_terms //array of author term slug(s),
                'operator' => 'IN'  //default operator ?
    
            ),
            array(
                'taxonomy' => 'language',
                'field'    => 'slug',
                'terms'    => $language_terms //array of language term slug(s)
                'operator' => 'AND' 
            )
        ),
    'post_type' => 'apk');
    
    $allargs=array(
    'posts_per_page' => -1,
    'tax_query' => array(
            array(
                'taxonomy' => 'author',
                'field'    => 'slug',
                'terms'    =>  $author_terms //array of author term slug(s),
                'operator' => 'IN'  //default operator ?
    
            )
        ),
    'post_type' => 'apk');
    
    $myquery=new WP_Query($myargs);
    $allquery=new WP_Query($allargs);
    
    echo allquery->found_posts - $myquery->found_posts;


  [1]: https://wordpress.stackexchange.com/a/233688/86197