I presume you've pulled or built some container images, yes?
The default size for the special system volume we create is around 5GB IIRC, and can grow to around 135GB.
If you run 'vctl images', are you seeing numbers that add up to around 10-11GB?
You could try vctl system start --compact or vctl system stop --compact to shrink the size.
-c, --compact Compact container storage upon start/stop