I have a question about the alcohol content of fruit wine kits.
My starting SG is 1.060 and after fermentation the SG is .990. Then after I add the F-pack, the SG is 1.020. So, what is my final percentage of alcohol?
Your ferment gives you about 9.2% abv. The sugar content in your f-pak does not affect the final abv unless you did not add sorbate resulting in refermentation. The dilution from adding the f-pak will lower the final abv a little.
The SG really tells you only the density of the liquid, and density is sometimes a good indication of the sugar content and so the potential alcohol of your must. After fermentation has ended the final SG gives you an idea of the relative sweetness of your wine not the alcohol content.
That said, anything you do that has a significant change in volume (significant, not small change) WOULD change the ABV because ABV is an abbreviation for alcohol by volume. So if the volume increased by 20 percent the the ABV would drop by 1/5. If the increase in volume is say, one pint, then in 5 or 6 gallons that is a quite small change (relatively speaking).