Changing signal at a fixed half-signal constant shows receptor saturation numerically. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Signal six gives one half occupancy
Hold half-signal at 6. Signal 6 gives occupancy 1/2.
6/(6+6)=21
Signal twelve gives two thirds occupancy
Raising the signal to 12 changes both numerator and denominator, giving 2/3.
12/(12+6)=32
Signal eighteen gives three fourths occupancy
Signal 18 gives occupancy 3/4. Three rows make saturation visible without a curve fit.