[Koha] Notices Documentation Question

Hello all, Up til now I thought (and I forget who told me thing) that all notices with the exception of the overdues needed to have the <<items.content>> notation to show the items the notice was talking about. Today I learned that this isn't true for the check out digest - and maybe others. Instead you need this notation: ---- "<<biblio.title>>" </b> by <<biblio.author>> (<<items.itype>>). Due Date: <<issues.date_due>> ---- The dashes included ... so what I need to know is what notices need to be like this and what use items.content and which use the <item> </item> tags? Thanks Nicole