The items.fine is a trick of our historical syntax. We need to provide a way to access this value from the a notice template using the TT syntax.
[% checkout.overdue_fine.amount | $Price %] feels like the 'right' syntax for this to me.. problem is, half the relations don't exist yet to do that.. and worse still we've not got the constraints either.
[% checkout.overdue_fine.amount | $Price %] would work for me - I imagine overdue_fine could be used to pull other values from the account line?