So I have an issue. I brewed last night, and took a gravity reading pre-boil and post-boil (well actually the post-boil was once it was dumped in the fermenter), but the post-boil was not what I expected. The pre-boil was 1.034, corrected for temp, with around 7.5 gallons of wort. After I dumped around 6 gallons in the fermenter, took a gravity reading and corrected for temperature, I mysteriously got a reading of 1.032? How is that possible?
I'm thinking one of 3 scenarios: I took the first reading wrong, and actually got a really low efficiency, I took both readings right (somehow?) and this beer is just going to be about 18 points too low (and about 2% abv short), or I got the second reading wrong and everything is actually going to be alright.
e: I guess the only sure(ish) way to find out is by taking the final gravity and multiplying by 4 (figuring an attenuation of 75%) to figure out the alcohol and OG.