Former indicates odd number, latter indicates even number. Could be used to reduce the number of symbols needed to identify a phrase in a code book. Proposed, but never actually used. Note that the operators at stations inside the divisions only knew the numerials, not how these mapped onto actual letters and phrases. More symbols and common words.
First signal gives line number, second signal gives page number.
Chappe added three additional parts to the code. Used a special signal, a horizontal double-crossed signal, to indicate the third part. Used a vertical double-crossed signal to indicate the fourth part. Borrowed a signal from the first part to indicate the fifth part. The regulator in this position is not a valid signal.