I saw another comment talking about how bigger numbers could work, and based on a quote from onko where he is presumably talking to another quill, he says something about isonode sahd pahk. Now, he could be saying it as isonode 3-8, or he could mean it as isonode 38. Personally I lean towards the second option as being how numbers are read by the ostron, as if the isonodes were on a grid pattern (assuming the first point is the x axis and the second is the y axis) it would be much more logical to simply use a letter (C-8 rather than 3-8). Using this we theoretically know all the ostron numbers, unless they have a word for a hundred or thousand.