Est final gravity calculation

How does beer smith calculate the estimated final gravity on the fermentation page?  Mine is always around 1.013/1.014.  I don't think I have finished that high ever.  I am usually around 1.005.  It's not a huge issue but I'm wondering if there is something I can change to make this number more accurate. 

BeerSmith primarily uses the average attenuation for the yeast selected (which obviously can vary), so you could change that number by altering the yeast min/max.  The other factor used is the mash temperature - lower mash temps will result in higher attenuation (and lower FG) for the conversion step of the mash.

Brad