Custom item number fields are fields that you can add to inventory records to track information specific to each item or workflow unique to your business. For example, you can track the status and results of quality control procedures specific to each serialized item, or you can track recall information on lot records.
These records include,
Serial numbered items
Lot numbered items
Gift certificate items
To create a custom item number field,
Go to Customization > Lists, Records, & Fields > Item Number Fields.
On the Custom Item Number Field page, custom field is listed,
Either we can edit an existing custom item number field or we can add a new custom item number field, click New.
Add necessary information. Example ,

Complete fields on the Item Number Field page as needed, and then click Save.
It can be seen in the specified item records.