In Diane Ackerman's The Zookeeper's Wife, why does the author use specific numbers or statistics?

In writing a nonfiction book, the underlying theme of which is the deliberate extermination of an entire people by the most technologically-sophisticated nation on Earth, there is a tendency among authors to be as precise as possible. The scale of death and destruction associated with World War II is almost unimaginable today, but that war was real, and those deaths did occur. Diane Ackerman's The Zookeeper's Wife, as with Thomas Keneally's fictionalized story about Oskar Schindler, the real-life German businessman who used subterfuge and no small amount of personal courage to rescue Jews from the Nazi concentration camps, presents a microcosm of a much larger event. The story of Jan and Antonina Zabinski's efforts to save a few hundred Jews from the Germans might seem insignificant when weighed against the six million Jews who perished, but it is the Zabinskis' courage and heroism that Ackerman sought to illuminate for English-speaking readers. Additionally, the fact that the setting of Ackerman's book is a zoo cannot help but create a somewhat surrealistic atmosphere. In order to emphasize the brutality and the reality of the true events she describes, therefore, Ackerman injects into her narrative a great deal of detail. Read, for example, the following three excerpts from The Zookeeper's Wife:

"Every bomb creates a different scent, depending upon where it hits, what it boils into aerosol and the nose detects slipping apart, as molecules mix with air and float free. . .Charred flesh and pine meant an incendiary bomb that blasted houses with a hot, fast fire, and that the people inside had died quickly."

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Poland's "outnumbered, obsolete PZL P.11 fighters posed no match for Germany's fast, swervy Junkers JU-87 Stukas."

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"Nazi bombers attacked Warsaw in 1150 sorties . . ."

The precision with which Ackerman relates the real-life story of Jan and Antonina Zabinski is demonstrated by the author's use of detail, whether in the physical descriptions she provides or in the use of numbers and statistics to inform the reader. We don't really need to know the precise number of German Luftwaffe sorties flown against Warsaw, but the use of the precise number adds to the author's credibility--no small thing in a nonfiction book--while ensuring that the reader is provided the requisite information with which to compare the scale of destruction and the imbalance of power between Germany and Poland. Authors of nonfiction history books (the late Tony Judt's Postwar comes to mind) use such levels of detail to emphasize the enormity of the events being described. Especially with respect to World War II and the Holocaust, the numbers are so vast, so overwhelming, that it can be difficult to visualize the extent of the suffering and destruction to towns and cities. The use of actual statistics, then, lends credibility to the author's work, provides important data that emphasizes the points the author is attempting to make, and enables the reader to better visualize the enormity of the suffering that occurred at the hands of Nazi Germany.