Volume is adjusted by 5% steps when using mouse wheel. The current visual meter shows approximately 17% steps; better to use same steps in visual information as in volume change. Speaker in background is not suitable, if user wants to control e.g. microphone capture level instead of playback volume level; better to have a selection of icons to choose from.
(In reply to comment #0) > Volume is adjusted by 5% steps when using mouse wheel. The current visual meter > shows approximately 17% steps; better to use same steps in visual information > as in volume change. Best to make the indicator continuous and make it show volume level as accurately as possible.
This is planned for 4.8.
With version 4.9.0 the plugin now uses the standardized icons for displaying the volume which has only three states and resembles the GtkVolumeButton widget. However this issue should be fixed now in a different way since the button provides a popup with a slider for adjusting the volume in a more fine-grained way.