Sequencing of customer numbers in CRM contacts

Question: 

How does the sequence of customer numbers under CRM contacts work?   

Answer: 

The customer numbers in be.ENERGISED are ranked by values. It is also possible to use letters in the customer number. This results in two different orders when sorting in ascending or descending order. Both results are correct.

 If you sort in ascending order, the numbers 1000-1019 will appear as the first result. After that the customer number 102 will appear and after that the number 1020. 

 In the end, the letters appear in alphabetical order. 

In case of a descending order, the customer number 999 is displayed as the first customer number. 

If all of the assigned customer numbers have the same number of digits, this problem does not occur. In the following example, all customer numbers have seven digits: