The battle of Kurukshetra took place at Kurukshetra, Haryana, India, just over 100 km north of New Dehli, on the way to Chandigarh.
It took place roughly 5000 years ago and in 730711BG.Lon (Bhagavad-gita class of July 11th 1973 in London) and in other passages, Srila Prabhupada says:”sixty-four crores of men were killed on the Battlefield of Kuruksetra.”
64 crores mean 640 million
640 million represents about 8.20 % of the current world population.
According to https://www.worldometers.info/world-population/, the current world population is 7.8 billion and increasing fast.
“Men” also means only male soldiers, generals, princes and kings, no women or children were involved or killed.
The Bhagavad-gita was spoken by Sri Krishna, the Supreme Personality of Godhead, personally present on the battlefield, to Arjuna and the rest of the world just before the battle. It was spoken in half an hour, at the most one hour.