The PIN will be the secret one that you use to get cash out, and you can use one card to buy multiple 'abonnements' to take out more than one bike. 150€ will be authorized but not charged on the card for each bike as a deposit, and then each 1€/1 day or 5€/7 day pass can be charged.
The first half hour of a rental is always free, you have to wait 5 minutes between rentals.