The calculated prescribed gain curve is just that, CALCULATED based on ideal conditions with audiogram info, fitting info, and hearing aid model info taken into account. And no ear canal irregularities are taken into account because they vary and they're unknown.
Don't forget what REM means -> REAL EAR MEASUREMENT. Real measurement, not calculated prescription. That's why a microphone is inserted into each ear canal -> to MEASURE the sound level from the speakers.
If you can plot out your "prescribed" theoretically calculated gain curve, and map it against the pre-REM measured gain curves, they don't necessarily match 100%. Usually the measured gain curve will tend to (but not always) underperform when mapped against the calculated/prescribed gain curve. The calculated/prescribed gain curve in theory should match more closely to the target, but not necessarily exactly either. That's because the target curve takes your audiogram info and run the calculation through the fitting rationale of choice to arrive at what the amplification level should be according to/as dictated by that fitting rationale. But the prescribed/calculated gain curve may or may not be able to achieve that goal, depending on whether the receiver is up-to-size or not, or whether the hearing aid has strong enough amplification for the hearing loss or not, or whether the dome is sealed tight enough, or whether your ear canal is too irregularly shaped or not, or whether the vent hole is too big or too small or no vent hole can affect it differently, too.
Anyway, as far as the clinician is concerned, they look at what their inserted microphone measures, and they see if that is at target yet or not, and if not, they adjust the gain one way or another to get as close to the target as possible, all the while looking at the measured gain curve on their REM equipment. For the clinician, the pre-REM curve is what was measured by the mics inside the ear canals before they change anything. And post-REM is the what the curve looks like after they change everything, and post-REM gain curve should match as closely to the target curve as possible. They don't look at or care about the calculated/prescribed gain when they do REM.
If the clinician doesn't take any of these snapshots of the actual real ear measurements (that make up the pre and post gain curves, and also the target gain curves) and/or share this information with you, then you wouldn't have it. All you would have then is the originally calculated/prescribed gain curve, and what the adjusted gain curve looks like on paper as required to match up the target. So in this case, your pre-REM data which YOU have is the calculated/prescribed gain, but it's not the pre-REM gain curve that the clinician was looking at during the REM process, because yours is the calculated one, his/hers is the MEASURED one.
As for post REM, same thing. What you have in YOUR record is what it took the clinician to adjust ON PAPER as a matter of record in order to see what is MEASURED on his/her REM screen. For example, on the measurement screen, at a particular frequency, the calculated/prescribed pre-REM gain is 5 dB. But because of under performance by your hearing aid, and maybe due to leaks from your bad fitting seal, the measure gain is actually measured at only 3 dB. And let's say that target is 6 dB. So the clinician would keep increase the gain 1 dB at a time until it matches the target. On paper, he/she should only click up 3 dB to go from the measured 3 dB to the target 6 dB. But because of the underperformance and leak, maybe the clinician actually has to click 4 dB up before the measured adjusted gain shows to be at 6 dB like where the target is.
So what you have for pre-REM is the calculated/prescribed gain of 5 dB. But what the clinician has for his/her pre_REM measured is 3 dB only.
As for post REM, the clinician had to do 4 clicks of 1 dB each to arrive at 6 dB target, so the clinician's post-REM gain is 6 dB as measured. But your recorded on paper post-REM gain is 5 dB (original pre REM), plus 4 dB upward clicks by the clinician to arrive at the target, so your post-REM on paper for the record is 5 + 4 = 9 dB post-REM.
So now you see why you're seeing 5 pre and 9 post on paper as calculated and recorded in actually adjustment in # of dB clicks (4), while the clinician is seeing 3 pre and 6 post, are all different? And that's why I wouldn't want to try to explain and over analyze why the pre and post numbers are different the way they are, because what you're looking at on paper in Genie 2 is not necessarily the same as what the clinician sees on the measured REM screen. So there's a lot of apples and oranges in the mix here. Why bother explain and analyze scientifically when it's actually too complicated due to many factors involved?
Even if I don't have the clinician REM measured pre and post gain curve, and I only have the original calculated prescribe gain curve and the final adjusted gain curve as what the clinician had to do to match target, I'll just take the final post-REM adjusted curve as recorded by the number of clicks done by the physician as a post-REM starting point to work off of. It doesn't pay to try to analyze so you can understand why the differences are what they are, because there are way too many factors and apples and oranges and cherries and vanilla all mixed up together.