1.312v would be right for that kind of clock speed.
Llc (load line calibration) is an option in bios which is left on auto settings will adapt voltage under load.
You will never see the voltage under windows match the core voltage in bios unless you disable llc in bios completely, which unless you are very experienced in overclocking is not a good idea.
1.312v under load is absolutely fine anyway as long as your temps are acceptable.