From a quick google search, I got barrons as making 23 litres, which is 6US gallons (or 5 gallons here in Canada). If you have a carboy from the US made for beer it should hold 5US gallons, whereas a wine carboy will hold 6US gallons.
Without knowing where you got your kit and how much you started with, I would say this is the result of using two different standards for brewing.
Welcome to my world. I am now stuck trying to convince hubby I should follow (and not scale) US recipes. He wants to know what happens to the other 11 bottles. (5US gallons makes about 55 bottles if I am right, 6US gallons makes 66 bottles.) Edit: after showing this to hubby I got the evil eye over the 11 missing bottles...just so you know (my apologies since that is very OT)
Reason: input from hubby