That is correct, and you can use as many anchor points as you see fit. If you enter a cut of 5 dB, that is -5, you may see exactly 5 dB drop but it will be close.
Since in your case the mini is apparently doing something good so just let it do its part but use Audyssey+App/Rat on top to help fine tuning. As you know, I don't use the mini anymore so for me I picked my anchor points based on the original REW plot post Audyssey calibration as reference and if I had to make a second Rat attempt, I would still go back to that original reference curve as I found that's the best way to perfect the final outcome. In your case, I suspect you can simply use your existing curve as reference and calculate the required cuts based on that curve. You existing curve is already as good as others posted on sites such as AVSF, but if you have time, it may be fun trying to make it look even better.