OK, I think I'm getting it.
Even though the shot should drive the number down, it wouldn't likely do it that quickly (2hr after shot), so the pre-shot number was probably low to begin with. The 1/2 can probably boosted the number, but the only real way to tell is by confirming a pre-shot BG level.
I'm filling out the Spread Sheet. I suppose the pre-shot should go in the +11 column in that it is 11 hours after the AM shot, and 1 hour before the PM shot?
The "preshot" number would go in the columns marked AMPS and PMPS. Most people will test the BG, then feed, then give the shot (assuming the BG number is high enough to warrant giving a shot). A 5-10 minute sequence of events.
Yes, the shot will drive the number down, but usually not until "onset" happens, usually 2-3 hours after the shot.
Here is what you would see in a "normal" 12 hour cycle:
AMPS/PMPS - the number would normally be "free from food", in that food shouldn't be given in the two hours prior to getting a preshot test. That way you know that carbs from the food aren't influencing the number
+1 to +2 - The number might rise during this period. Because the food will be pushing the number up before the insulin starts to push it down
+2 to _+3 - Prozinc should be reaching the onset point, where it will start pushing the number down
+5 to +7 - The insulin should be having its biggest effect, and the BG should go as low as it will likely go that cycle and reach "nadir".
+8 to +12 - The BG is most likely coming up because the insulin should start to wear off.
+12 - that would be AMPS or PMPS, when it's time for the next scheduled shot.
Of course, lots of things can change, it wouldn't always look this simple. Food given during the cycle can affect the numbers. Sometimes onset and nadir will happen earlier or later than expected. Duration might be longer or shorter than 12 hours. But in a perfect world, that's what a PZI/Prozinc cycle
should look like.