These settings were most recently expanded in firmware version v1.2.0 - see firmware page for how to update.

The WOLFWAVE has a volume knob to control the output volume, plus a setting for adding a fixed gain/attenuation to this (i.e. adjusting the output volume produced when the volume knob is turned to max).

There are also settings for more fine tuned control of output volume and output mixing:

The gain of the headphones and speaker outputs can be adjusted independently, which can be a useful way of limiting the maximum output power to a comfortable level.
The relative volume of left and right headphone channels ("L/R balance")
Which channel the speaker is connected to. The headphones output is stereo, but the speaker output is mono. By default, the speaker uses the same audio as the left headphones channel. This can be changed with the "Speaker channel" setting. In most cases the audio data for left and right is the same, except if binaural mode is on, L/R balance is not zero, or CW regen with stereo split is on.
Swap left and right channels ("Swap L/R").

The output settings can be found in the menu under "Other settings > Output settings".