I'm struggling with this too.
I have a recipe which states an OG and ABV. When I add the measurements, ingredients and timings to Brewers Friend it seems the value for Efficiency is critical and alters both OG and ABV significantly.
So in the end I used the Efficiency value to calibrate the OG and ABV to the stated values in the recipe. Ended up with an effiencecy of 71 in that cell.
My worry would be, if that turns out to be lower than the efficiency on the day (not sure how this is measured) the the ABV could jump to say 8.5% when it should be 6.5, or more likely go then other way and I end up with a lower ABV
How do I ensure efficiency hits the 71% required to achieve the correct ABV?
Am I missunderstanding ?