There are no extract values for acid malt because it has no extract potential. Acid malt is used only to lower the pH of your mash. I use it for a step infusion mash for my lighter color beers. The darker beers don't need that acid malt due to the dark malts, which contribute to a lower pH. Don't use over 3% or you run the risk of your final beer having a sour malt flavor.
Gordon Biersch Kansas City