NAV Productin Forecast does not take sales orders into account

Hi experts,

I am using NAV 5.0 SP1.

I recently implemented production forecast into NAV to generate demand to drive supply. And as I noticed, NAV is not taking sales order into account.

I have an item which is Make-to-Stock, with Prod. Order replenishment system, and Lot-for-Lot reordering policy.

I input production forecast from June to December by week in the Production forecast worksheet. Then in the Manufacturing Setup window, I set the Current Production Forecast field with the worksheet I just put the forecast in.

Then I run the MRP+MPS plan for the item. System generated orders exactly based on the forecasted quantity. For example, I have forecasted a quantity of 10 for week 25, system generated planned production order for 10. But with in this week, I also have a sales order for 1. System didn’t consider this sales order fell into week 25, and planned exactly what the forecast quantity is.

My understanding is that: forecast - sales orders = total demand. But the system is not giving me the right plan. My sales orders are not consuming the forecast.

Is there a fix for this problem? Or am I missing some setups? Please help.