<<...>>Should I forget the norm and let them sit until day 28 as
instructed, or should I
rack and top off with similar wine? I'm mainly concerned because my
6
gallon carboy leaves way too much room below the neck.
One other quick question...On day 30 is says to rack into a 5 gallon

carboy. Shouldn't this be a 6 gallon as in the start on day 1?

Nick-
Racking at the end of primary fermentation really does two things -
it gets the wine from a vat or plastic tub into a container that is
more easily sealed (to prevent spoilage by exposure to air), and it
removes the wine from contact with the gross lees (grape
skins/seeds/stems, etc.). Following Jack's instructions, you don't
need to rack again at day 7, because the wine is already in a carboy
and (because this is a kit wine) you really don't have gross lees,
since you are starting with just juice. Your lees are only yeast
cells, and there is no special urgency to rack the wine off them. If
you still have too much airspace after adding the gallon of reserved
juice, by all means, top up with water or a similar wine.

Yes, on day 30 you do want to rack into another 6-gallon carboy. The
instructions on day 30 currently (as of today, August 25) refer to a
6-gallon carboy - perhaps this was a recently-corrected typo? In any
event, you want to rack into one or more containers that can be
properly sealed (with an airlock). If you are starting from actual
grapes or other fruit, you can sometimes get so much sediment that
racking from a 6-gallon container to a 5-gallon container makes sense.
In the case of kit wines, you shouldn't lose nearly that much volume,
so it generally makes the most sense to rack into a same-size carboy,
and top up with water or similar wine.

Doug