In writing one decision that the writer has to make is how specific to be on something. There are people who hate specificity with the heat of a mainstream star of O9 classification. (The heat of a million suns.)
This topic came up when someone looked over my book where a plot point had the Nazis trying to crack the human genome with the latest Hollerith Tabulating machines. I took the speed of the machine and the number of calculations it would have to do and came up with the time, 3 trillion years. Instead of saying 3 trillion years it was suggested that I just mention it would take longer than my character wanted.
Naturally after doing the calculations to find out how long it would take I wanted to leave the result in there. But I also looked at it from the reader's side. Anything over 50 years was too long, so the exact number didn't matter to the plot. However, when I read science fiction I like it when there is a grounding in real math.
I ended up compromising and having the Nazi tell my character that it would take a long time, and my character responded, “According to my people longer than the life of the sun.” Most people can't really grasp the difference between 5 billion years and 3 trillion years. It is still an awful long time.
I'm wondering how do you feel about specificity in fiction?