Optimizer and Configuration for Available Date for In-House Order

Hi

I am in trouble about Optimizer and Order Date.(Avail/Req Date)

[What I want to do]
After executing Optimizer, Order date for in house should be middle of the Month.
# Time Bucket is Month

[Current situation and Configuration]
Currently the order date is always middle of the month. (eg. 15th June 2013)

Configuration

1.SNP Optimization Profile
Bucket Offset During Production: 0.5
Bucket Offset During Shipment: 0.5

2.Product master/ Lot Size Tab
  Period Factor:0.5
  #It seems this value is nothing to do with Optimizer
   This is only for Heuristic.

Someone, please advice me if you know other neccesarry configuration.

Regards
Ryo