Your account is no different than anyone else's as far as the AdSense goes. It's not a bug in the system because not a single other person has had a problem. My guess is you are copy/pasting it or typing it wrong.
Then give a correct example, the one you have in your interface is not correct. It has too many digits, plus a period.
The period is intentional, the number of x's was never meant to be exact. But since you seem to think that it wants you to enter 20 digits after the pub-, I changed it for you so you feel better.