That's the key, all treaties are worded such that they can be interpreted in many different ways.
@Enquirer, can you lay off your condescension and bravado for a bit? Let's not turn all discussions into slangers. We are not Pakis or commies.
It's most likely to be be Astra. Air launched Brahmos is a possibility but I would have expected a NOTAM slightly longer than 355 km, unless they are testing air launched Brahmos for a range of 290km.