Question about the pressuredrop in the example aneurysm

Hi there.
Recently I am checking on the aneurysm, and I found that:

T inletZpos = util::roundToInt(inletCenter[2]) + 1;
Box3D measureBox(lattice->getBoundingBox());
measureBox.z0 = measureBox.z1 = (plint)inletZpos;
T inletPressure = DESCRIPTOR<T>::cs2 * (boundaryCondition.computeAverageDensity(measureBox) - 1.);
T pressureDrop = inletPressure * util::sqr(dx / dt) * fluidDensity;

So the pressureDrop would be the pressure on the inlet I guess?
But on the page 11 of the paper ‘Palabos: Parallel Lattice Boltzmann Solver’, I found the description that:

The pressure drop between inlet and outlet

I’m kind of confused, isn’t that should be calculating pressure on the outlet and get subtraction?