Dissociation Of Sequence & Clause Complex: Clause Complex Realising Figure

Halliday & Matthiessen (1999: 125-6):

On the other hand, a clause complex may in principle correspond to a figure rather than a sequence.  This happens through grammatical metaphor of an interpersonal kind: an interpersonal modality that would be realised congruently as a modal auxiliary (can, may, will &c.) or a modal adjunct (perhaps, probably &c.) is ‘upgraded’ to the status of projecting clause in a clause complex; for example:

I don’t suppose || there’s very much                             ‘there is probably not’