Lot size by period in PP run in SAP APO

Hi,

I need one clarification for PP heuristic run in APO.

I have set PPDS horizon as 2 days in material master.

Lot size procedure by period 1 W

Demand at DC are

D1    D2   D3  D4

10    20    30  40

My expectation that PP will only consider the demand in PP horizon and will generate 10+20=30 purchase req whereas i am getting output as 10+20+30+40=90(adding all demand in 1 W)

Please suggest if this is correct behavior.

Thanks,

Krishna