Those are nominal rms values, the range is plus or minus 10%. I am not sure where it comes from but in the US it's not uncommon for supplies to be referred to

Those are nominal rms values, the range is plus or minus 10%. I am not sure where it comes from but in the US it's not uncommon for supplies to be referred to as 220/110 rather than 240/120. They're generally understood to be the same thing.