Query regarding Purchase Order Lines stored in database?

Hi Friends,

While i extract Purchase Order details ,i found that in demo database,some Purchase order lines are stored in seperate entries in POR1..

eg: if <b>21</b> A00001 is ordered,then the purchase Order line for 20 item is stored in a row and purchase order for 1 item of that same item 'A00001' is stored in a seperate row in POR1..

In wht criteria SAP B1 take it as a seperate row for a single item order while storing in POR1--Purchse Order Lines

Thanks in Advance

regards

Sooriyakala.P