MMOREL,
A little bit of Simple maths:
The bond duration is 36 months(3 years),the amount is 50.000$ For a new type rating.
BUT for the first 18 months they will deduct 50% of the total bond amount from your salary(50.000$/36 monthly, for 18 months).
This 50% will be refund to you after 3 years from your date of joining.( not applicable in your case if you decide to leave before 3 years.
So if you decide to leave after 2 years for example ..you will basically still have to pay (50.000/36)x 12( prorated ) on top of the 50% that has been already deducted from your salary for the first 18 months.
50%+33% = 83% of 50.000$=41500$ that you will have to leave to the company if you leave after 2 years from you date of joining.