In a static fluid, pressure grows with depth as P = rho * g * h, because a deeper point carries the weight of more fluid above it. The linear climb means doubling the depth doubles the gauge pressure. The exact value holds only for a uniform fluid with constant density and gravity; real columns have density variation, surface motion, and depth and calibration uncertainty.
A clean hydrostatic column binds density, gravity, depth, and pressure. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Depth closes the hydrostatic ledger
Density 2, training gravity 10, and depth 3 metres give pressure difference 60 pascals.
2×10×3=60
The clean gravity is a training value
This book uses training gravity 10 so the pressure ledger stays exact.