Cadence pss pac iip3 ipn

1） LNA do IIP3 simulation , how to set Input power Extrapolation Point (dBm）？

2） Input power Extrapolation Point
Why have this？ what does this mean？

IIP3 point is not a real point, it's an extrapolated point that's why an extrapolation is done to find out the xIP3 ( even xIP2 etc)
For that reason, this field should be filled by minimum power level which has been applied to the system being as variable power.
But if the linearity has some strange behaviours due to model accuracy or other reasons, in that case extrapolation point can be found by lowering and augmenting...