# VAE sampling during test time [duplicate]

On page 11 of this VAE tutorial it is said that new samples of the data distribution X can be found by plugging z ~ N(0, I) into the Decoder P.

I don't understand why this is true. During training, in order for f(z) to approach X in distribution, z was sampled from N($$\mu(X), \Sigma(X)$$) [as seen on page 10]. So how does sampling from ~N(0, I) at test time work.