Everyone try to understand. 400km away the Chinese non military vessel was asked to leave the area according to an Indian source. 400km away from nearest Indian land is not considered Indian waters. Indian military and government have no power 400km away from nearest Indian land. The vessel is non-military. Maybe it left because it was done with the job, maybe it left because the Indian navy around the area was disturbing the mission, and maybe it left because it felt threatened by armed military vessel.
That's all there is to this report. The really interesting idea to know is what its mission was. Testing military related acoustic equipment or observing things? What things? Was around strait of Malacca and closer to Malaysia and other south east asian country than India. Maybe Indian navy went this distance to push the vessel away because India somehow knows what the purpose of the vessel is since hundreds of Chinese ships sail even closer to India because it is a trade route. Take a look at the belt and road ports. All of them are using Indian Ocean routes and position much closer than 400km. This means Indians thought this ship represented some risk or collecting something sensitive information.