Under 10. Discussion they discuss the lack of numbers and how they're using CONS as a kind of 'add 1' and CAR/CDR as a kind of 'subtract 1' when calculating pos

Under 10. Discussion they discuss the lack of numbers and how they're using CONS as a kind of 'add 1' and CAR/CDR as a kind of 'subtract 1' when calculating positions in memory, similar to how integer index/pointers might be used on a different type of machine, as if the length of a list would be an implicit pointer. They seem almost giddy about having designed a computer that can perform interesting mathematical tasks like integrals and derivatives without numbers.