dukeit's a typo error.Instead of 3 point 84 kilos [3.84] it's...

duke
it's a typo error.
Instead of 3 point 84 kilos [3.84] it's been transcribed as 38.4 kg/car.
Thus a million vehicles need 4 mil [rounded] tonnes
right?
Logic also suggests that no battery is going to weigh 38.4 kg graphite plus 19 kg lithium equals approx 58/60 kilos.

duke some super models weigh less than 60kg!!
certainly a purposefully built light weight designed car isn't going with a 60kg Battery.
no it's 3.8 kg graphite and 1.9 kg lithium for a 6 kg battery.

so yes you have to take care of experts typographical errors.
It's all part of an individual's Comprehension ability that with all due respect duke you could do with some work on.

cheers