Previously, in order for the notes displayed on the ER-101 to match what you hear coming out of your VCO, you would have had to tune your VCO so that 0V produced C0. Now you can tune your VCO to any chromatic pitch and adjust the ER-101 note display to match.
If you tuned your VCO so that 0V corresponds to 27.5Hz (or A0) then you would adjust the ER-101 root display note to 0A.00 to have the note display consist with what you are hearing.
The 1V/oct standard only encodes pitch intervals (or equivalently frequency ratios). This means that 0V could be arbitrarily assigned to any pitch and then after that all the other pitches would be exactly determined. This situation has led to different manufacturer’s assigning different pitches to 0V. Any 1V/oct device with a tuning knob has this “problem” as well as MIDI-to-CV devices and 1V/oct sequencers with chromatic note displays.