brewers friend acid malt no effect on pH

[Neptune]

I'm using brewers friend advanced calculator and when I put in a pound of acidulated malt (3.1% of my grain bill) it is not budging the calculated mash pH at all... I threw in 10 pounds just to see if it moved the pH calculation and it only moved the pH down .01.

I'm doing full volume biab starting with 16 gallons...

Any idea what I'm doing wrong?

EDIT: Nevermind... I had the 16 gal in the "total water volume" instead of the "mash water" field.