DFPlayer Library - What Does This Command Do??

I've been looking through the full example code for the DFPlayer and I can't work out what this function is supposed to do?
myDFPlayer.outputSetting(true, 15)
The comment says enable output and boost gain... But what output is it enabling / disabling?
From what I can tell of the schematic for the DFPlayer, there is only one output coming from the MP3 IC (YX5200) and that's from DAC_L and DAC_R which is broken out to two pins but also feeds the input to the Mono Op Amp for the Speaker....
So does that setting enable / disable the DAC_L and DAC_R on the YX5200 and change the gain?
Thanks.
myDFPlayer.outputSetting(true, 15)
The comment says enable output and boost gain... But what output is it enabling / disabling?
From what I can tell of the schematic for the DFPlayer, there is only one output coming from the MP3 IC (YX5200) and that's from DAC_L and DAC_R which is broken out to two pins but also feeds the input to the Mono Op Amp for the Speaker....
So does that setting enable / disable the DAC_L and DAC_R on the YX5200 and change the gain?
Thanks.