OK, so the only meaningful one is the recipe in question: Partial mash grain and extract.

Important info from recipe:

BHE: 72%

Batch size: 5.5 gal

Trub loss: 1 gal

Grain: 8 lbs Pilsner at 1.036 contribution

Extract: 5 lbs DME at 1.045 contribution

Given your BHE and grain bill, you have 8 lbs at 36 points for 288 gravity points of grain.

At 72% BHE, there are 207 gravity points in the fermenter

Per gallon, this is 207/5.5 = 38 gravity points per gallon.

With one gallon of trub, there would be 38 points lost to the trub from the contribution of the grain.

That means that 207 points plus 38 points, or 245 gravity points are in the post boil volume.

Your extract will give you 5 lbs at 45 points for 225 gravity points.

If the extract is added to the boil, then 100% of this is in the post boil volume.

This contribution of 225 points plus the grain contribution of 245 points gives you 470 gravity points post boil

Your post boil volume is 5.5 gal in fermenter plus 1 gal trub loss or 6.5 gallons

470 gravity points in 6.5 gallons is 72 gravity points per gallon or a target of 1.072 target final gravity

Since this does not match BeerSmith's prediction, we will tackle it another way:

245 points from the grain in 6.5 gallons gives a gravity point contribution of 38 gravity points per gallon

225 points from the extract **in the fermenter volume of 5.5 gallons** gives us 41 gravity points per gallon.

This total is 79 gravity points or an OG of 1.079, which** does match BeerSmith's prediction**

So it appears you are correct in your assertion that the program does not calculate this value correctly. The best thing to do at this point is to copy this to Brad so that he can look at the way the program calculates out the OG value for partial mash. He has commented that he is working on some fixes right now for a update of the current version of BeerSmith (which does do the calculation the same was as BS2), so this would be the best time to let him know of the issue.

This is why attaching a recipe demonstrating your issue is critical to verification or helping to understand BeerSmith.