OK, I took another look and realized I misinterpreted how the before & after adjustment are represented. The full horizontal length being one lap and the six selected laps overlaid, of course, stupid of me not taking the time to understand. I saw the first “straight” richer than the next two and jumped to confusion. But everything else I said stands, I think. The data point markers look like automatically selected max/min which have zero relevance to an AFR curve. The scaling is so compressed that even if there is the expected change in AFR it would be difficult to discern. Heck, at that scale the line width alone covers a significant range. And I still don’t grasp the meaning of those last two columns. Someone please educate me.
In the AIM software the Blue "down" triangle and Red "up" triangle represent that Laps lowest and highest recorded values during the Lap. The "right pointing" plain triangle represents the "average" value for the data in the Lap. The round colored dot and the adjacent numerical value represents the value in that lap where the cursor is located which is at about the 320 foot mark. With this information it is not necessary to guess what numbers the lines are showing and if this were in AIM software you would be able to move that cursor to any point of interest that you wished to see the numerical values without having to guess.
As described, and reading the numbers for Fuel Pressure and A/F ratio, the Pressure starts out at around 55 psi for the first 3 laps and then the next three it is around 52 something. Next the A/F ratio for those three higher pressure laps averages about 12.62 while for the next three laps at lower pressure, averages 12.40. So, it does show that in fact the pressure was decreased and the net affect was that the A/F ratio did get richer by about 1/4 ratio.
So at this point the question is do you believe the data and try lowering the pressure in hopes of seeing the A/F get richer? Don't count on it, but what you may need to think about is what else might have been going on. How long did you take to make the change? Did you shut the car off while making the change? How hot was the car running before and after the change.
While you were making your change appropriately with the regulator adjustment, the ECU may have been countering your change in response to other factors. I doubt that there was a sudden drop in barometric pressure going on so I tend to lean to the under hood sensor environment conditions that could be working against you. I have found over the years that the ECU curve tends to overly lean the calibration as you go up in altitude and that when going from a lower altitude to higher I have to increase the fuel pressure regulator rather than decrease it as expected. Also, I much prefer using the Lambda scale as it reports the mixture balance as being plus or minus to 1 with less (0.9) being 10% rich or 1.05 being 5% lean. When using A/F you need to know what the Stoic value actually is for the fuel you are running in order to know what A/F ration you want to target. If you are running expensive race fuel, you can find that on their web site but what are your chances of getting from the local gas station or even for fuel pumped at the track if it is not a known vendor.