2011 SolidWorks Help - Creating Bills of Materials from Parts or Assemblies

http://help.solidworks.com/2011/English/SolidWorks/sldworks/AllContent/SolidWorks/Core/Detailing/t_BOMs_Creating_Bills_of_Materials_from_Parts_or_Assemblies.htm?id=cf02a6a237ff419fbaeffe5204428573#Pg0

Now manual set a1(a2,a3,a4), see next fig.

Help with set a1(a2,a3,a4) of link BOM..