Firestore documentation and the quotas chart show that a document can only be updated about once per second. Why do I seem to be able to update a document more than once per second with no problem?

I tried a simple "for loop" and all writes seem to go through:

 const db = firebase.firestore(firebase.app("prjID"));
 for (i = 0; i < 10; i++) {
     console.log(`updating /test/test with test:${i} ${new Date().getMilliseconds()}`);
     db.doc(`/test/test`).update({ test: i });
 }

log shows :

I am wondering if someone knows the supposed server response when multiple write operations are attempted in less than a second i.e, beyond the limit that I seemingly can ignore?

If I am missing something and the limit means something different any explanation?