I think that isn't defined as a writing system as you can only record numerical data.
Same as how the Inca Quipu[1] isn't generally defined as writing, despite the fact it seems they may have encoded some non-numerical information such as provinces for accounting purposes - like having a province_id in a database.
You can keep track of taxes etc. with a system like Quipu, but you couldn't write down the Iliad with it.