/**
 * Increase comments-per-page limit when viewing spam comments.
 *
 * @see WP_Comments_List_Table::get_per_page()
 *
 * @param int    $comments_per_page The number of comments to list per page.
 * @param string $comment_status    The current comment status view. Default is 'all'.
 * @return int The filtered number of comments to list per page.
 */
function wpdocs_spam_comments_per_page( $comments_per_page, $comment_status ) {
	if ( 'spam' == $comment_status ) {
		$comments_per_page = 50;
	}
	return $comments_per_page;
}
add_filter( 'comments_per_page', 'wpdocs_spam_comments_per_page', 10, 2 );