calclulating how much alcohol using beer smith

I have a recipe in beersmith for a 5 gallon bath that should be around 4% alc.
I want to make it a 2.5 gallon batch with the exact same ingredients and quantites so it would double the feremtables. I would think the alcohol % and OG would be doulbe in BeerSmith but when I change the Recipe batch size from 5 gallon to 2 gallons nothing changes????

Why??Thanks!!

The first question... did the weight of ingredients change to reflect the reduced volume? If you used the recipe scale button then the program thinks you are trying to get the same final numbers in a smaller (and/or larger) batch therefore reduces the amount of the ingredients used to make the final numbers come out to the same. Hope this helps.

When I change the batch size, my estimated ABV changes.

I'm not try to end up with the same % alcohol. I am trying to make half the size but double the alcohol with all of the same ingredients.

Where do you change batch size in BS?  I changed it on the first tab page that comes up from the recipe. Do have to hit a button to make it recalculate?

Simply changing the recipe size on the design tab should change the final numbers. I was talking about the scale recipe option near the top next to IBU and OG adjust.