On the FVW wine log there is acalculation for ABV based on Initial and Final SG readings. (IG-OG)*135.9. This calculated result doesn't matchdirect measurement from the hydrometer. Example: assuming the initial SG is 1.1 and the final is 1.0, the calculated ABV is 13.59 instead of 13.2 from the hydrometer. Am I doing something wrong? Which is most correct? What do our experts use?