How to get subscription quantity?

Hello, I am currently developing a project with WordPress and I am using Woocommerce plugin to offer subscriptions to my users. I need help on how to get the quantity of a subscription on PHP.

I am using this code to get subscription but I can not retrieve quantity:

$subscriptions = wcs_get_subscriptions( array(
        'customer_id'            => get_current_user_id(),
        'subscription_status'    => 'wc-active',
        'order_by'               => 'DESC',
        'subscriptions_per_page' => - 1
    ) );