Acidic is used to reduce your plants pH level. To grow the perfect plant you need the perfect conditions and your plant really cares about its water's pH levels. Bottle 1 and Bottle 2 are allies that work together to make sure that your water is balanced and your plant happy.
Tip: If you’re finding that you’re using too much of this it’s probably because you’re using tap water instead of distilled water. Use distilled water to improve pH consistency.