How much time has elapsed between the atomic bomb explosion and Miss Sasaki’s observation of Hiroshima in the first paragraph? How does this relate to the description of the plant life at the end of the paragraph?

I'm not sure about the time elapsing. Here is the first paragraph from the text:

At exactly fifteen minutes past eight in the morning, on August 6, 1945, Japanese time, at the moment when the atomic bomb flashed above Hiroshima, Miss Toshiko Sasaki, a clerk in the personnel department of the East Asia Tin Works, had just sat down at her place in the plant office and was turning her head to speak to the girl at the next desk. At that same moment, Dr. Masakazu Fujii was settling down cross-legged to read the Osaka Asahi on the porch of his private hospital, overhanging one of the seven deltaic rivers which divide Hiroshima; Mrs. Hatsuyo Nakamura, a tailor’s widow, stood by the window of her kitchen, watching a neighbor tearing down his house because it lay in the path of an air-raid-defense fire lane; Father Wilhelm Kleinsorge, a German priest of the Society of Jesus, reclined in his underwear on a cot on the top floor of his order’s