When your card was declined you also saw this in the error message:

"WARNING TO DEBIT & CREDIT CARDHOLDERS:

Please limit your purchase attempts. Every time you attempt to make a purchase, your bank temporarily puts the purchase amount on hold. It can take your bank 3-5 days to unblock access to credit card funds, and 5-10 days to unblock access to debit card funds."

That explains why you see the $18.88 listed on your account. No funds have been taken, it is merely put on hold by the credit card company.

Hope this helps. PM me if you have further questions.