pressure gauge fault?

Hi I have a remeha avanta 28c plus and the boiler is working as it should, but pressure gauge shows low and I have been told by a fitter that the gauges are useless and not to rely on them, and that the plus models have a digital pressure read out; could anybody let me know how to get read out ? When I turn boiler off at mains and then turn back on what comes up on the middle digital screen is P2.3 and F1.4 is one of these readings my digital pressure ?; then when press R it goes through normal sequence of 1, 2, etc finishing with 0 and then will work quite normally. Thanks for your help Gary