There is no such thing as full volume, and there is not such thing as zero volume.

To be fair, since we can go to +3dB out of 0dB, we could also go to 200% on a 100% scale. In the era of software it would not be completely insane to allow users to choose how their faders are marked. (It would be insane to use 3/4 of a slider's travel for the range 100% to 400%. So the locations of the markings on usable sliders would remain mysterious to %-only folks.)

Ultimately people who use this a lot would choose to become familiar with dB, as they always have. But there's no rush.

‘There is no such thing as zero volume’ - can you expand on that?

Surely constant unchanging air pressure has zero volume?

Volume is the range of variation in air pressure, right? That can surely go down to zero.

It can also only meaningfully go up to about double the absolute mean air pressure, before what you are talking about becomes shockwaves of overpressure.

I don't know what you're talking about. Both of those exist.

Zero volume is when a speaker's diaphragm is still. On an 8-bit PCM audio file, it corresponds to a value of zero.

In the context of a signal, full volume corresponds to the 127 value in an 8-but PCM audio file (or arguably -128). In the context of a speaker, those values should push the diaphragm no further than how far it can travel linearly without distortion. Obviously the user may want to turn down the volume from this full volume.

I hope you understand that even when using an audio editor that displays values in dB, the underlying values are integers (or floats) that absolutely have zero and "full volume" meanings, and conventionally map respectively to -∞ dB and 0 dB.

There such a thing as going to 11.

https://www.youtube.com/watch?v=uMSV4OteqBE