I topped off at 4 gallons rather than 5. Am I wrong for thinking this is low despite not adding more water? I'm now a day after fermentation began. I plan to do a secondary fermentation. How much sugar should I add during the second fermentation for an 5-6% ABV beer? Thanks in advance!! First time homebrewing!
If that is truly your OG and not current SG, then the problem is likely with your measurement. When you top off the wort is heavier than the water and sinks to the bottom. It's really difficult to get them mixed, no matter how much you stir. SO when you take a reading you're getting it form the watered down portion on top.
That is very low OG. It will only be about a 3% ABV beer. Which is fine for some styles like a Scottish Light / 60.
Its possible it's done fermenting now. Leaving it in secondary will not increase the abv unless there are still sugars to ferment.
Maybe the 1.030 SG reading is what you have right now. In that case it's not called your OG anymore. OG is Original Gravity before any fermentation. If your SG is 1.030 then it needs to stay in primary a few more days.
Double check your recipe. It may have been indented as a smaller 2-3 gallon batch. Or like brewchez said, not mixed well when gravity reading was taken. If the OG was only 1.030