how do we know that our marks for MHT CET 2019 has been increased after we have raised an objection

There is no official way to know if your marks have increased. Many students raise a query in the get paper. Almost 127 this year. Not all of them are found to be legit. You do not have any way to know which of the ones or how many of them are correct.  Also,  it might so happen that according to the answer key your answer is correct,  but someone challenged it and the answer got changed to something else and you lost a mark there. That is also a possibility. So it is not known if your marks have increased or decreased.