Question about Esophageal pH (Bravo pH study being done now)

I'm currently undergoing the Bravo pH 48-hour esophageal acid exposure test. For the test, I've decided to revert to "bad" eating habits, to put myself under enough stress to show anything there might be to show.

I'm wondering, how normal is it for esophageal pH to drop below 4.0. (What's a normal level of acid exposure?) I'm not trying to manipulate the tests results, I'd just like to understand what I'm seeing, if it's even worth understanding.

The monitoring device I have on me now is quite interesting in that it not only displays the time, but also displays a pH reading. I've noticed that the pH on this thing has gone from ~8.0 to as low as 1.8 (may have gone lower, but I hadn't noticed). Most of the time (easily 90%+) it goes between 4.0 and 7.8, with the lion's share of that being in the upper ranges, though one time, right after implantation, I had a cup of cold water and the pH dropped to 2.8 for a few seconds. (Dirty water?) And last night I had an incident in which the pH reading bottomed out at ~1.8, and spent no more than a few minutes under 4.0. (Had eaten pizza a few hours before, and was now sitting in a slouching posture.) I presume that means acid exposure, but is that brief a level of acid exposure "normal"?

One thing's for sure, if the readings in this thing are what I think they are, then my symptoms are almost entirely NOT caused by prolonged acid exposure, at least not that the monitor's picking up. After some pizza yesterday I've felt as if my throat was burning. (The main reason I all but gave pizza up to begin with.) The burning feeling continues to this morning; I wish I could chew some frigg'n gum! Yet according to this thing my pH is bouncing is sitting at 7.1 as I type this.

Thanks in advance.