Product labels and MSDS include terminology that might be unclear. Sometimes, the words have special meanings under the federal Hazardous Communication Standard. Other times, they're easy to get confused.
A case in point is keeping straight the meanings of acid, base, alkali, and caustic. The last three all mean the same thing. So do you buffer an acid with a high pH solution or a low pH solution? It might seem logical that a low pH is a base, given other uses for the word base (e.g., the base is at the bottom). Actually, the opposite is true.
To dilute a substance identified as a base (caustic, alkali), don't add something from a container showing a pH of 12.0. You need to add an acid (low pH), instead.
To avoid confusion, use the first letters at each end of the numerical scale. "A" comes before "B", so it goes on the left (near the "one").