A comparator rail may still lose voltage through output resistance before the load. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The output rail still has source resistance
The comparator rail is 12 volts, but the load receives 8 volts.
VL=8V
The output power budget closes
The load current is 2 amperes. The load power is 16 watts and the source resistor power is 8 watts.