For an Indian Managing Director, that is a sizeable investment. What is unclear is whether this is part of his compensation from the company, or bought from his own money. Ideally, it would be from his own money, as an ESOP kind of a grant need not appear on a stock exchange's announcement list.
If the Managing Director is putting so much of his own money into HDFC, then that is a great endorsement of this stock.
HDB 1-yr chart