That's probably closer to the total of the4 Nagaski and Hiroshima bombs combined, IIRC. Not even the notorious John Hersey put the number that high for just Hiroshima.
Estimates I’ve seen have Hiroshima at 135,000 and Nagasaki at 64,000, but there are numbers all over the map so you could well be right.
I guess the main point is to put them in context of the huge numbers of deaths from conventional fighting and bombing at the very same time. The atomic bombs focused Japan’s attention because of the spooky nature of one weapon doing so much damage in an instant. The death toll itself is something Japan seemed to willing to accept with resignation. Glory for the Emperor.