Safale US-05 attenuation

[kalkunipraed]

Brewersfriend uses 75% as US-05 attenuation. I am getting consistent results in the range of 79-82. This matches the official spec sheet value of 81%. Why is it like this?
I sometimes forget to update the value in the recipe and miss on the intended FG.

 

[Ozarks Mountain Brewery]

sorry so late I didn't see this, its an average I'm guessing for the novice mostly that doesn't follow the steps we do.

for best results always use yeast nutrient, no matter what people say and plenty of oxygen, you know air is not just oxygen so shaking a carboy is not necessarily giving the correct amount for the yeast to survive and they can just run out and stall, there is no overkill in adding oxygen in my book