iExpense - Expense type and Attribute_category

Hello

Can someone please explain the relationship between Expense Types and ATTRIBUTE_CATEGORY column of the AP_EXPENSE_REPORT_LINES_ALL table.

For certain expenses, the Expense type value gest stored in the ATTRIBUTE_CATEGORY column. For some expense types, this column is blank, but the ITEM_DESCRIPTION column gets populated.

Any thoughts/reasons.

Thanks

Len