The Narayan numbering system, as with most Narayani things, is tied to the concept of the Lattice Tree.
It is pictorial, and each numeral represents a tree. Much like the D'ni Numerals it is a base-5 (quintary) system: Number 1 is represented by a tree trunk (i.e. a single vertical line I) with higher numbers indicated by additional branches; number 3 is a trunk with 2 branches (i.e. like Y); the number 5 is a fully grown tree. The number 10 is a 5 with a semicircle topping it.[1]
Saavedro used this system while paging his journal.