Front applies both. Rear only the rear. If you have pressed front before the rear it puts pressure in the system for the back brake so if you then put your foot on the rear brake it bites at a higher point. Now I know what to do to get the higher pedal position. I will experiment with applying the front and then applying the back then releasing the front whilst keeping the back on. It does make a huge difference in slow speed control and is much more controllable in the higher or pre pressurised position.