Solved by googlebot in post #4 
              
              
                You’d sample from prior if you don’t care which digit you generate. 
Basically, clusters should overlap at zero. Your picture has too few points too infer contours. Should look like there: How well does $Q(z|X)$ match $N(0,I)$ in variational autoencoders? - Cross Validated 
Re: quantiles, I just mea…