Any list can have an automated numbering scheme that will populate each new item.
For example, if you need Projects to utilize a numbering sequence, simply add the setting and fields described below and the sequencing will begin with the next item added.
Configuring
Add a Single Line of Text column field for each list a numbering scheme will be created for, such as “Project No.” for Projects.
Once the field is added to the appropriate list it is only necessary to add the field to the item’s Display page as, the user will not be required to edit it. Search the Display page editing section for further details.
Add the following Setting to the Advanced Settings list.
Setting Name: AutoNumberFields
Setting Value: [ListName]|[FieldName][Numbering Scheme]
Note: each list has its own row in the Setting Value box.
Note: The Auto numbering scheme will only update items going forward starting with 1. More details can be found here: http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.strings.format.aspx