Subtracting the buoyant force from a body's true weight gives its apparent weight, the reading a support actually feels while the body sits in that fluid. That subtraction holds only for a stated fluid density, displaced volume, gravity, static equilibrium, and simple geometry. Real apparent-weight readings also reflect body shape, wetting, density variation, scale calibration, surface motion, and uncertainty.
Apparent weight is the checked difference between weight and buoyancy. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.