What is the usage of Cache given under AR Document Sequencing?

Summary:

Content (please ensure you mask any confidential information):

We have configured Document Sequencing at the ledger level with the type set to Gapless, and in Receivables System Options, the document number is set to “When Completed.” Additionally, we enabled the option “Copy Document Number to Transaction Number” for the DOO transaction source.

The Issue:
Because of this setup, the Transaction Number in AR is different from the Invoice Number in OM → Fulfillment → Billing. Here’s why:

When the transaction is first created through OM, it receives a system-generated transaction number.
When the transaction is completed in AR, the document number is generated and copied to the transaction number.