Lower pH, period. If you wanted your mash pH to hit 5.3, and it does, then you have succeeded. The only other concern is whether you've used too much acid and the pH is lower, maybe 5.0-5.1 or something. If that's the case, then obviously the beer might end up with an odd tartness. All just educated extrapolations, I am not a water expert ala Palmer or Brungard (sp).