Client 800 System Access Method

Today, I learned about SD to the ELE. Me customer data and found that the customer's internal code seems to be all defined internally. I created a customer in cient000, and its internal code is actually 1, which is funny. I want to unify the code into five digits and end with C. For example, 4063c does not seem to work. When querying the kna1 table in the background database, we can see that the original customer data is almost none in client000! There are more than 800 million in seven thousand!

So I wanted to create a client user, but I couldn't get into ddic. In the end, you have to use the sap * account to enter the default password 06071992 or pass. I want to use spro to configure and see if I can customize the encoding rules...