The 30,000 number in the blog is the number of changes landing per day, not per month!

I am not sure what it is you are saying. What I am saying: I would have supposed that Claude writes 99.x% of Claude's Code code, and that ~no code at Anthropic is written by humans anymore.

to achieve what?

Honestly not sure that there are that many effective changes a day given how little complexity there is to their public facing product.

No. 90% sounds like a low number. That implies something else is writing 10% of the code? People? Other models? What on earth is writing that other 10%?