I brewed up the brewer's best double ipa yesterday following instructions and topped off with about 2g of water when i placed in the fermenter. I took my sample reading with my fairly new refractometer. The refractometer is one of the inexpensive $30 type ones which i calibrated with distilled water. My og measured at 1.071sg / 18.4 brix. The recipe says it should be about 10 points higher. I did not take a hydrometer reading due to a time crunch. I know i topped to about 5.25g but not topped so much to make a 10 point difference, could the scale be off on a refractometer for og?