I guess that is softwares shortcoming. It is typically pretty accurate otherwise. I had a Common projected to finish at .014 (mash60m @ 150.)I did a 45m rest at 144 then 30m at 153 and got it fermented to a perfect .010. I also let the fermentation freerise 2c at the end. Not sure which was responsible but I’d like to repeat the result
i'd guess do the same process and you will likely end up close.
thats one of the benefits of really getting to know a yeast well. once i have about 4 batches down with one type of yeast, i can go through the processes/grists/temps etc and get a feel for what the attenuation is on a less fermentable grist(my mashes are all the same, 150f infusions) vs. an all base-malt grist or with sugars.
but yeah, as denny said, the software is just guessing based on the not-always even accurate suggestions of online data/yeast manufacturers' estimations on AA.
make your processes repeatable, and go from there