If you top up with wine after racking to glass before fermentation is complete, you might add enough sulphite and sorbate from the topping up wine to halt the fermentation. You do not want that. Some kit instructions actually specify water.
the very first batch my dad and i made looked like a cross between
cherry and grape kool aid. only hade 3 gals. but was about 14
percent when swissed in a glass it would go up the side and stay
and was not sweet. good red appertiffe wine though.
