[jetrink]

Can't you just ask it to set the volume to a specific volume as a percentage, like 38%? This works on Google Home. In the Google ecosystem, it also usually works if you ask it to raise the volume by a small increment like 5%. (Other times, this sets the volume to 5%.) I think you also used to be able to ask the device to raise the volume 'a bit' or 'a lot', for 5% or 20% respectively, but that stopped working a long time ago and I haven't tried recently.

If neither of these work, then I am very frustrated on your behalf.

[mgraupner]

Unfortunately it only knows integers and rounds 15% up to 20% and 12% down to 10%.