the relations between due date and ending date in MPS/MRP?

fjhxl

Now one end user complain the interval between due date and ending date of Sales Order and Forecast after MPS calculation.

In our system, the interval are normally 1 week. But this time we found the interval for some forecast change to 3 weeks and the interval for SO keep 1 week.

I read some document and realzie that safety lead time and default safty lead time in Mfg setup will affect the interval, but we didn't setup any safety lead time.

Howerver I am not sure how to define the interval 1 week in which repport or codeunit and other setup can cause the interval?
(navision attain 3.01B)
Any ideas? Thanks in advance.