If you short at 4500 points, your margin is (calculated by 15%): 45000 * 300 * 0. 15 = 202500. When the stock index futures fell to 450 points, you earned 4050 points: 4050 * 300 = 126544.
However, it should be remembered that in the field of financial investment, behind any profiteering, the same huge risks are inevitably hidden. The core of trading is to control risks rather than profiteering!