At fixed area, pressure changes the checked force without changing the surface. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Four pascals over three square metres gives twelve newtons
Hold area at 3 square metres. Pressure 4 pascals gives force 12 newtons.
4⋅3=12
Six pascals gives the eighteen-newton audit force
At pressure 6 pascals, the same area gives force 18 newtons. This row matches the pressure-force link used by the audit.
6⋅3=18
Eight pascals raises the force to twenty-four newtons
Pressure 8 pascals over the same 3 square metres gives force 24 newtons. The diagram asserts area-averaged pressure only.