InRoads XM - Spiral Geometry

InRoads 08.09.03.06

I have a compound clothoid on my geometry. I calculate p=3.78 using the formula p=Ys-R(1-cos(SpiralCentralAngle)) and even measure it graphically at 3.78, but the results show 3.02.  What formula is being used in this case, and why?  I get the correct results for p with a regular clothoid, but it appears a different formula is being used here, which I assume is because it is compound.

Thanks. Chris