Yes, your output driver should be set to 100% for most cases. This is because the Digital Power Station driver becomes the default playback device while Bongiovi DPS is running.
When you control the volume on your computer, the Default Playback device is receiving the volume control. That is why we set the hardware device (in your case Realtek) to 100% when Bongiovi DPS starts. Volume control settings are transferred to Digital Power Station. You can learn more about how it works here.
If you do not want your Realtek driver to be set to 100% automatically, you can uncheck “Auto Adjust Volume” in the SETTINGS tab.