Vague and a little glitchy
My understanding of this app was you input your water chemistry and the beer style you wish to brew and the app outputs the necessary additions of salts and/or acid to produce the ideal brew water. It does not, exactly. You have to tinker with the additions and see if it actually works to raise/lower the ion concentration of your water. It's way more complicated that it seems. And it just shuts down for no reason quite a bit.