If you're making your Paypal account or are adding another credit/debit card on it, they will have your card paid $1.99. It's just a customary process to confirm if your card is valid, you'll receive it back soon. About the pin code, you can check the credit card bill to see the number. Or, if your card company has a text-message service, it's very convenient to get. When you make your Paypal account or add another credit card, you can receive the text message including the number. Incidentally, whenever you make a payment with your card, you'll receive the text message. It can be a safeguard to protect you from fraudulent charge.

Hi, I think this PIN number you are referring to might be your italki PIN password, which is used for withdrawing cash and trasferring money from your italki account to your Paypal or bank account. It is specified when you submit your teacher application on italki.