Without knowing the subscription ID to give you a 100% absolute answer, my best guess is that you had a signup from a trial joins.
They show an initial charge of $0.00, then rebill if the customer does not cancel the subscription. You can see an example of one by visiting
SexArt, and looking at the red Free Access button on the right.
If you'd like me to look it up by subscription ID, I'd be glad to. Just drop me a line in email.
