This setting allows us to configure an auto-incremental numbering feature for some of the out-of-the-box entities. We can change the prefix text and suffix length, as we can see in the following screenshot. Only these two fields are editable. We can use up to three characters in the Prefix dropdown, and we can select different length options from the Suffix Length dropdown. The following screenshot shows how the settings look:

We can also see a preview of the changes after modification. Once these settings are changed for a particular entity, the system will generate an auto-number for the entity, based on the new settings. When a new record is created, for example, in the preceding screenshot, the configured auto-number prefix and numbers will be used to generate new contract record auto-numbers.