It will be OK
I just got the limited edition Nebbiolo through the stabilization stage, and added no water.
The grapeskins kits give a little extra; that is there is some juice in the grapepack, and it completes a little above the 23 litre mark on the primary. by using a little extra dilligence at racking, my italian carboy (a little over 23l) was almost filled. When I racked before stabilizing, I did not use the sediment bowl, and as a result carried over more wine for stabilization. In fact, de-gassing was a challenge, and I had to get most of the gas out before adding the chitosan, and could not quite get all of the second pouch into the carboy! Upon racking off the sediment, I racked to a mexican carboy (exactly 23l) and had some headspace. I added 500ml of Barolo (that stuff is expensive) to the carboy to top it up for bulk aging.
By the way, there is a topping up instruction for bulk aging; it's hidden in the step 6 bottling instructions. Huh!