Lori,
Before you continue you may need to know a few things not made obvious in Don's reply: firstly, and obviously, the Status flow in Manufacturing is not subject to the rules you see in Sales and Purchasing. The values applied are arbitary although it is common practice to use numerics in Manufacturing and it flows in sequence, ie, 10, 20, 30, 40, etc., NOT 40, 30, 20, 10.
Only code "99" is hardcoded. Therefore the meaning of "40" and "41" are meaningless in terms of software. These are purely flags to indicate something that should mean something to your Business. Yes, they can be set to be updated by R31410.
However, the key element missing from this string was the mention of the FPO Processing Option in R3482/R3483. Check this out. There is a reasonabley good White Paper on this in the KG. In a nutshell, this Processing Option prevents the explosion of Planning Messages to the Components of Work Orders at (or beyond) the FPO Status.
On the Supply/Demand Inclusion Rules. Normally all the Statuses are Included as Supply/Demand up to the Fully Complete Status. The only exceptions are where you wish to take something out of the Demand Pattern in order that MRP Re-plans the Supply. This can happen if you are considering scrapping a batch of WIP, for example.