Delivery Cost in a Purchase Order

Hi Experts,

Could you please help me with this query? I am looking at a standard PO (ME23n) and in PO history tab for line item 10, I find a Delivery Cost Document posted along with a GR document. Both these doucuments have same number.(There are invoice documents posted as well). I checked the conditions but Header and Item conditions for delivery cost have Zero value against them. My question is from where and how system is calculating this delivery cost? What I know is that incase of planned delivery cost, there has to be consition type setup and cost is mentioned at the time of PO creation and incase of unplanned delivery cost, it is posted at the time of invoice but not sure which one is the case here as the delivery cost condition types have no value.

Thanks,

Syd.