I think this is my second or third time reading through while waiting for updates & after finally taking notice of the triangle based numbering system that's shown on page 1 of this chapter, I find it pretty interesting.
At first I thought it was split into 10, like bowling pins, but then I realised that 0 = empty & 9 = full. So the triangle is split into 3 layers horizontally, with 1 mini triangle at the top layer, 3 mini triangles at the middle layer, & 5 mini triangles at the bottom layer.
The number represented depends on the amount that is coloured in
It's a clever little system, but I'm just wondering what the symbol for a decimal would be, if changed at all.
Might use it for a fantasy setting of my own.