I need to create a shortcode for display CPT posts. I want to add an atts that print the number of posts_per_page I need in the args for Wp_query. But If I use [short_events number=5], it print only one post. Where I’m Wrong?

function dis_short_events($atts, $content = null){

ob_start();
$numero = extract(shortcode_atts(array(
    'number' => '-1',
 ), $atts));

$args =array(
    'post_type'=>'eventi',
    'posts_per_page' => $numero

);

............
 add_shortcode('short_events', 'dis_short_events');