Hi,
Thevenin equivalent circuit might be an interesting way of calculating some values.
Ignoring the capacitor and Zener, whose individual series resistances you'd need to find to locate the missing 253uA from my calculations:
R11/(R10 + R11) = voltage across R12 = 2.951V seen at GPIO input.
Current out of R12= voltage across R12/R12 = 2.952V/11,500 = 0.00025668 A = 257uA into GPIO
PD R12 = current through R12 in Amps squared x R12 value in Ohms (0.000257 * 0.000257) * 11500 = 0.000760W = 760uW
For PD in R12 it should be R0012 I + Zener Iq + C0016 I, maybe adding GPIO input resistance when high-Z and when on (if figures available or can extrapolate from other figures) might be interesting, also checking R12 current is enough for ZD005 at over-voltage events by using e.g. 30V as input to R10 and calculating from there.
I guess that sim shows 2.953uA as missing 253uA are going into Zener and capacitor, maybe.