My doctor told me that most people get Hep B, and their bodies are able to fight it off on its own in most cases. This might leave antibodies behind that might be what is showing on the test. I know my doctor knew from my labs that I had hep b previously and fought it off. It was Hep A that my doctor said I needed to get a vaccination against. (there is none for Hep C).
So, from what you have said, I don't think you have to worry. (but I am by no means an expert on the subject)