[css-break] Breaks and list items

Break inside/after says: "Always force a break (of all possible types,
through all fragmentation contexts) before/after the principal box" and
"any" has similar text. How does this work when an element generates more
than just a principal box? CSS 2.1 gives list-items as a case where this
can happen, but isn't very clear on how it works. Is the additional box
before, after or in the principal box? The explanatory sentence isn't very
helpful: "These additional boxes are placed with respect to the principal
box." If a list item has 'break-before: always' is this text sufficient to
require that the break happen before any non-principal generated boxes (for
example, a counter)?