Welcome to the tech age, I have been doing this for a while now...
Where are the numbers stored?
CC numbers are not stored anywhere. The tokens are generated once when u add the card and then the tokens are stored on a secure chip on the phone, similar to the way fingerprints are stored for TouchID. Tokens is likely why not all cards work yet - the banks/networks are the ones generating the tokens and need to support it
Why can't the cc# be stored on this secured chip ?