How do I config a mixer with 2 values

[GM-Script-Writer-62850]

This is in my MPD config file

audio_output {
        type            "alsa"
        name            "ASUS DGX Analog Output"
        device          "hw:CARD=DGX,DEV=0"     # optional
        mixer_device    "hw:DGX"
        mixer_control   "Headphone"     # optional
}

This is my hardware volume control

amixer -c 0 cget numid=15 200,250
numid=15,iface=MIXER,name='Headphone Playback Volume'
  ; type=INTEGER,access=rw---R--,values=2,min=0,max=255,step=0
  : values=241,241
  | dBminmax-min=-125.50dB,max=0.00dB

When i use mpc volume [VALUE] to set the volume the left/right end up not synchronized (eg i may get 0,200)

This is what it looks like in alsamixer: