Auto Pay - My check has 10 digits but the xfinity system only takes 9 digits

On my check it has 10 digits for the account number.  On the Xfinity website I'm trying to setup auto pay but it's only takes 9 digits.  Of course calling Customer Service it takes you round and round and none of the option resolve this problem and you can't speak with a human.

How do I add a auto pay with 10 digits for the account number.