pHAT DAC volume control retropie

I have installed the drivers as described and can here sound through headphones. However I have wired up a small speaker but can barely hear it. How can I adjust the volume I’m software?

Any ideas on this? I still can’t get the sound to work properly. Also in the retropie sound menu the volume appears to be at zero. I increase the volume but when I leave that menu and return it’s back to zero!