That boost controller is probably measuring/displaying in kg/cm2 and not psi. There are conversions on the net.
If you hit the high button with the ignition on, it will display your high boost setting for a few seconds before looking for your present high boost readout - which will be 00.00 if you don't have the motor going. You can do the same with the low boost button.
Not sure, but I think it is a HKS III evc. Definitely HKS, could be a II, not sure. You will be able to download a manual for it from the Usa HKS web site.
Pwr is power on/off, mode is the switch to go to different setting modes [time, boost level etc]. and Sbc is your scramble boost - basically a high boost hit. So if your normal High boost is set at 1.2 kg/cm2 and you want to up it for a short time [say 30 seconds] then you set Sbc up to your nominated high hit [say 1.6 kg/cm2] and it will boost to that extra level for 30 seconds while you pass another vehicle or something. You will rarely use it unless your racing, and unless you have a built engine, it is likely not a good idea, it would stress a std motor.