Beer Smith Question

[Workie]

I've recently got my hands on Beer Smith. I'm havin fun with it, trying different things and new ideas. But one question I have is... If Dextrose is fully fermentable (which I thought it was) why when you enter it into a recipe using Beer Smith does the Bitterness Ratio change?

I've clicked on 'Add After Boil' but it still seems to have an effect on the Bitterness Ratio.

I've still got heaps to learn. So this may be a simple question, but I'm still curious to know the answer.

Cheers.
Workie