From Audacity manual:
When the mouse pointer is over the scale it changes to a magnify icon.
- Left-click in the Vertical Scale for any Waveform or Spectrogram view to zoom in. […]
- Hold Shift and left-click […] to zoom out progressively. […]
The scale mentioned is the part of the screen just to the left of the waveform, where -1.0
, -0.5
, 0.0
, 0.5
and 1.0
are shown. You can zoom out and see the range from -2.0
to 2.0
.
Your screenshots use different units. The -1.0
to 1.0
scale doesn't use dB. To change the scale use Audio Track Dropdown Menu.