Hi Pedro,
this column to my understanding is relevant only for role type items on access request and is not relevant to system. If you would like to have system line item type being approved by an specyfic Agent you need to define separate path for this kind of line items in your initiator rule and next assigned an agent (user/user grp./ etc) to approve this kind of items.
Details how to do this are documented:
GRC Request with both System and Role Line Items
Regards,
Filip