Previous Purchase of Online Class Price Adjustment

I have previously purchased your online class to find out if I actually wanted to try worm composting. I understood that if I purchased the class and then decided to purchase the worms, the price of the class would be deducted from the worm purchase price, but I do not know how to get the price adjusted on paypal. Would you please tell me how to do this?

Thank you,
Tracy
Answer from BigTex Worms:
You pay for the order, then I credit your purchase the $5. Please be advised this coming Monday (6-25-12) is the last day for me to ship until fall. The weather is getting too hot.