MRP RELEASE DATE FOR SMALL PARTS Before and After Release of Parent

Hi to All    Using BPCS 405CD.     Have a question concerning MRP due date of 
child part planned order before parent planned order is released  and MRP due 
date of child part planned order after parent order  is released. Child part 
planned order  has due date of one day before parent, when parent is a planned 
order. If the parent gets released before the child part is released, after MRP 
has run the child part planned order part due date changes to the start date of 
parent

.  Why does the  due date for the child change to one day later after the 
parent is released?  The start date for the parent is the same when the parent 
is a planned order and when it is a released order. But, now instead of the due 
date for child part planned order being day before the parent start date, the 
due date of child part planned order is day of parent start date.  Why does the 
due date for the child part say the day before the start date of the parent 
before the release of the parent order and day of the start date of parent 
after the release of the parent order?   Would appreciate any help.   

Judi Svoboda
Ridewell Corp