Try this without $i = 0;
<?php $popular_days_ago = '$popular_days days ago'; $recent = new WP_Query(array( 'posts_per_page' => $number, 'orderby' => 'meta_value_num', 'order' => 'DESC', 'meta_key' => 'post_views_count', 'date_query' => array( array( 'after' => $popular_days_ago )) )); while($recent->have_posts()) : $recent->the_post(); ?>