You are still 'seeing' the Col C figure as a limit - it is not. It merely enables you to see the available extra payload when the figure is less than A and B. You CANNOT 'bust' Col C at any time - you CAN, of course, bust MZFW. Col C consists of an unchanging MZFW figure PLUS fuel loaded so cannot ever be 'busted' and payload does not enter the equation. Payload only appears when you have selected the 'lowest of the three'. Adding payload will not change MZFW! Adding fuel merely increases the figure. Similar to Cols A and B in that respect - they cannot be 'busted' since they are both based on unchanging Max values (apart from Tanks and Trip fuel). Look at the whole matrix, as I said, as a Dispatcher's/Load Agents piece. Both their and your, the pilot's job, is to monitor and ensure that no actual 'limits' are exceeded, while ensuring enough fuel and maxxing the payload when necessary..