Multiple delivery schedules in PO

Hi

1) How does the multiple schedule lines generated in a Intercompany STO Purchase Order.

Ordered Qty is 10.

Delivery schedule (Tab in Item Details)

Schedule line 1 - confirmed qty 0 and open qty 10

Schedule line 2 - confirmed qty 10 and open qty 0

2) Dates in both line also appears the same, then what makes to generate the 2 lines.

3) Is the delivery schedule line are manually created ?

thanks

MM