The instance word is the graph block with one entry appended. The compressed sparse row block is self-delimiting — its own header determines its length — so nothing needs to separate it from the parameter, and the split of the word into the two parts is determined by the word itself, not chosen. The parameter comes last so that the graph block sits at the same offsets as in every other statement built on this encoding.

The format is defined here, next to the encoding it extends, and the statements made on it live in the proof packages that import it rather than restate it, so that every bound stated over it is a claim about literally the same inputs. Its first consumer is in this submission's own proof package: the bounded search tree of Downey and Fellows, which decides vertex cover within c · 2^k · (|x|+1) steps over this format.