Go to Application Settings -> Application Setup -> Number Series Relation

Here the details about the relation between the Forms/Screens and the Document Series, also find the General Accounting Setup and its Mapping with the system’s default Document Series.

See below screen shot, the series ACS that is mapped to General Accounting Setup.

To edit and modify the mapping of Document Series to specific Form/Screen, click on the edit icon and follow as mentioned below

You can have multiple Document Series for one Form/Screen. If both are mapped, both will be shown while creating new record. You can make one as default.

Note: When Create

The marked row is the new Document Series shown above can be mapped to General Accounting Setup and make it default.

After mapping, you can see the new Document Series for General Accounting Group as shown below

Once mapping is done, navigate to 

Home -> Account -> Posting Setup -> General Accounting Setup -> Add New and see the changes as shown below.

Check and select 

Below is a sample entry (for testing the newly created Document Series).

Once you save the record, below you can see the new Document Number

When creating next record, the new Document Number will be GCA002ACC

This is how the Document Series can be created and used throughout the application software. The same procedure is applicable for all other Forms/Screens.