When does the ADVANCE_ID field get populated on the PS_EX_SHEET_HDR?

After adding a cash advance to the expense report, it is supposed to be linked with the expense report. After saving and/or submitting for approval, the ADVANCE_AMT on the PS_EX_SHEET_HDR is updated correctly with the advance amounts that were applied to the expense report.

However, the ADVANCE_ID is not updated with the Cash Advance ID that was applied to the expense report. When does this field get populated with the appropriate advance ID? I've noticed that it remained blank even after the expense report got paid.