Include in cost roll up flag in Bill of Material for Config item

Hello All,

When ever a config order is place , and a star item i.e config item is created via Autocreate config program, it will create BOM & Routing for the star item, if we check the BOM for given star item for some of the items under the BOM will have include in cost roll up flag as checked and for some unchecked.

Can some one pl explain as from where does the system default/derive  this cost roll up flag value.

Thanks

Manoj