If I might be so bold, why not show a calibration Delta T instead of a calculated one?
The calibration Delta T temperature is shown in other graphs. This particular graph was intended to show the temperature contrasts.
This is Slide 9, here:
It is similar to the Slide 7, except that Slide 7 has actual calibration data for 50 W. I do not have any calibration for 216 W input. I probably have 200, 250, 300 and so on, but not 216 on the nose. So I have to extrapolate.