Thanks 4Feline!
Charlie has had both of those tests. They're just really bad with their paperwork there and it concerns me, that's why I want a second opinion. Once, the receptionist stuck Charlie's ID sticker on another patient's file...had I not noticed and pointed it out to her, well who knows? Now, the doctor who initially told me he has FIV is telling me that it's FeLV. If there's any chance that this is an error, it's worth it to retest him.
Thanks again for your help.