RMS AMPL
110VAC = 156
120VAC = 170
220VAC = 311
230VAC = 325
240VAC = 339
A lot of people making mains EC circuits use alternating supplies with the amplitude setting on whatever their "mains" voltage is, which isn't accurate. This is actually the RMS voltage, which is a lower value than the amplitude. To convert, just multiply the RMS value by sqrt(2) (~=1.414).
It's not something you want to get wrong, since you're looking at a minimum 30% error on any measurements, and worse for power calculations.
