This value is displayed as it is collected through the Source Collector / File Import and is equivalent to the Record ID of the record collected.. Should you wish to change this value, the Source Collector will need to be updated or the data (Record ID) will need to be updated on the import file. Once you have made this change, all records collected through the updated Source Collector will display in the updated format selected.
Read this article to see how historic data can be updated as well.
Refer to docs.varibill.com for more information on Source Collector attributes.