I have searched the web and found a very comprehensive guide regarding BOM and the way you can handle and process the items in this category. The file is in PDF format and can be downloaded from the link below. I have made it Goo.GL compatible because it's hosted on a FTP and the link might appear broken when pasted, but I assure you it's the correct URL.
Note: You can find all the information you need in that file. Additionally, make sure you have a compatible PDF reader installed on your computer.