The audio options UI allows to adjust volume only in increments of 5%. But what really surprised me was that it’s not possible to override that by editing the setting manually - when you set it to 2% the game will treat it as 0%, but when you set it to 3% the game will treat it as 5%.
Why? If you don’t want the stock UI to allow players to fine-tune the volume, then at least allow addon developers to do that.