Sometimes when a payment fails to complete, the pre-authorization charge applied by PayPal to check the availability of funds will remain "pending" on your card or bank statement. This amount (the base course fee, without GST) will disappear from your statement, typically within a few days.
Completed transactions should generate a receipt (sent by e-mail to the address you provided to PayPal), and will be in the amount of the course fee, plus any applicable taxes.
If you still have concerns, feel free to contact us -- we are happy to review and refund any actual duplicate transactions!