It is better to disable controllers completely if assigning in FSUIPC, as P3D has a habit of re-assigning controllers which can cause issues.
This is nothing to do with the curve, it is due to your calibration.. The minimum value calibrated is 4534 for throttle 1, and 3272 for throttle 2. Axis ranges usually go from -16384 to +16383, so you are losing more than half your axis range. Calibrate the minimum value correctly.
The reason you only see the right-hand part of the slope is explained in the User guide:
Also, for future reference, please always attach your FSUIPC ini file when you have any issues with assignments - this tells me a lot more than images do (including which version of FSUIPC you are using, which you didn't mention!).
John