Assuming you are using
whole crushed grapes less stems and
Lalvin K1 V1116 yeast and
transferred most of the sludge (less seeds and skins) to a 5 gallon
carboy secondary,,,, then
How many 1 gallon secondaries should I prepare for topping off the
carboy during racking (s) to wind up with 5 gallons at bottling ?

I read on Keller's site to move the sediment to the carboy when I
transferred the primary to the carboy secondary. Apparently there is a
lot of viable yeast in the sediment. Don't know if this made a
difference but the carboy is producing 20 big "gaaaloooop" bubbles a
minute in the airlock. The SG was 1.022 at 85F when the wine went into
the carboy yesterday on Wed the 22nd.

BTW a newbie "DUH"
I tried a neighbor's idea to use my 80 qt Coleman cooler as a primary.
36 hours after pitching the yeast I opened the cooler to punch the cap
down and my once 75F must was now 95 F !!
"DUH", coolers are good at retaining cold AND heat (smile,,,,)
Left the lid open and covered with a towel after cooling things down
to 85F with an ice pack.
Temp stayed right at 85F - 87F. Now that it is in the carboy not sure
what the temp is. The yeast did not seem to mind one bit.