The volume can be adjusted on several places. Perhaps, you already knew this.
1. On the player program e.g. VLC or the website during browsing e.g. Youtube. This volume setting is not synched with Windows in anyway.
2. Windows (the realtek using synced with Windows volume setting)
3. If you are using a headphone/Headset with volume setting e.g. on the cable or e.g. if the loudspeaker is self amplified without built-in DAC. This might be also not synched with Windows volume.
Usually, I set the volume e.g. on VLC and Youtube max @50% and I am leaving the volume on my Z623 @40%. I do not touch those ever again.
I adjust then the volume only from Windows from 0 - 100%, 50% Windows volume usually already max for my ears.
This setting is...