@RpiBeginner just wanted to point out that your screenshot is 'aplay -l', and the instructions say 'aplay -L'. You need the capital L option to get the right output. That will allow you the correct name of the audio card.
Each audio card has one or more audio mixers (audio devices) on the audio card. Emulationstation needs to know which audio mixer to use on the audio card when you do the volume up and down. To find that out you need to use 'amixer scontrols -D <AudioCard>', where <AudioCard> is replaced by the name of your audio card you got in the previous step. I know from your screenshot that your audio card is set to the 'default', so you should run 'amixer scontrols -D default'. That command should show you the correct name of the audio mixer on your 'default' audio card. It will most likely be called 'Digital' or something like that. Please note that you must copy the name exactly as it is printed.
Those two commands above will give you the settings you need.
The first command gives you the name of the audio card you select in emulationstation, which is 'default' (based on your screenshot).
The second is the name of the audio mixer (audio device) on that audio card, which you'll need to run yourself to get.
That would be all you need to get around for most things... Except video sounds. RPI uses OMX player to play the sounds from video files, and they need a third setting! This setting looks different again from the ones we got earlier. The format is:
'hdmi:hw:0,0'
That setting will use the first mixer on the first audio card for video sounds. If that setting doesn't work then you should try 'hdmi:hw:0,1', which will use the second mixer on the first audio card.
Hopefully that will give you all the information you need right there. Remember that if you cannot select the setting directly from within emulationstation you can add the setting directly to the es_settings.cfg itself . Please see the instructions page I linked to earlier for more details if you need to do that.
Hope this all helps! Good luck.
Tminit