I know this is obvious, but.. My wife just helped me lug my second batch down to our storage room where my first batch from last week is hanging out. She points out "this bottle is bigger". Woops. There were 2 carboys in the kit my LHBS put together for me and I never had them next to each other since it was all in 2 boxes. I assumed they were the same and last week I had measured out 5 gallons exactly in the first carboy to clean it and made a note of where that level was. Foolishly I used that information today. So I basically just topped off my 5 gallon recipe to 6. I know its tough to get a good reading with an extract batch mixing it up in the fermenter and all, but I did take one before pitching and it doesn't seem too far off, 1.047 and the recipe range was 1.050-1.054. I'm sure I'll find a way to choke it down. Lesson learned, time to plan the next one.