IBU calculation question

So I built a recipe that uses 1 oz of Fuggle for 60 min and 0.5 oz Styrian Celeja at 15 minutes.

Beersmith calculates the IBU as 0 for a 3 gal batch.  If I change the batch size to 6 gal and double the hops without changing anything else the IBU calculates out to 29.7.

Any idea why?

I even adjusted the 3 gal batch recipe to use 16 oz of each hop.  The result in calculated IBU?  0.4

This is driving me nuts.  Thank you in advance.

export the recipe as a .bsmx file and post it.  It is hard to figure out what is going on when we cannot see how the recipe is built or the process you are using.

I think it's fixed now. oddly enough I took the same recipe as I entered for a 3 gallon batch and created a new 5 galon batch in Beersmith (with the amounts of everything adjusted for 5 gallons.  I then used the 'Scale Recipe' tool to move it to 3 gallon.  Then it worked fine with an IBU of 28.1.

Enter as a 3 gallon > IBU calc all wacky.
Enter as a 5 gallon and scale it to 3 > same recipe I entered the first time, but with an IBU more that 0.4 calculated.

Yeah fun!