How the two-step test works
The test asks for two notes: hold your lowest comfortable note for about a second, then do the same for your highest. Pitch detection runs on your device as you sing each one, converting what it hears into a frequency in Hz and then into the nearest note name and octave, the same way a tuner identifies a note from an instrument. A held, sustained tone gives the detector a stable signal to lock onto; a quick blip or a sliding note is harder to read accurately.
From those two notes, the tool works out your range two ways: in octaves and semitones, and as a comparison against typical voice-type ranges. The semitone count is just the interval between your lowest and highest note, and the octave figure is that same interval expressed in whole and partial octaves, so a two-octave range shows as exactly that rather than an odd number of semitones.