Swedishguy It would help if you quoted the exact wording of the transcript. I certainly can't seem to find that section online, and I assume you have seen it somewhere, so please copy and paste it here.
The reason why it is important is that the following links cast doubt on the claim that anyone at Nuremberg would have suggested 840,000 Russian POWs being killed there.
http://www.jewishvirtuallibrary.org/jsource/Holocaust/Sachtrial.html
Also the following link which goes into more detail:
http://www.scrapbookpages.com/Sachsenhausen/Trials.html
Some excerpts from the link (which appears to contain a transcript from the trial of Anton Kaindl, the camp's last comandant)
Public Prosecutor: How many prisoners were exterminated in Sachsenhausen while you were commandant of the camp?
Kaindl: More than 42,000 prisoners were exterminated under my command, this number include 18.000 killed in the camp itself.
Public Prosecutor: And how many prisoners died by starvation during this same period?
Kaindl: I think 8,000 prisoners died by starvation during this period.
Note that Kaindl was in charge of the camp from at least 1943 and possibly August of the previous year (the only page I can find on him is in German so I'm not sure) up until its evacuation. It seems unlikely that in the face of this evidence that either the prosecutors or Kaindl himself would be suggesting that between 1936 and 1945 some 840,000 Russian POWs were killed in the camp when Kaindl only talks about 50,000 prisoners of all types during 42-45. On the assumption that Kaindl took control in 1943 that still leaves only around 2 years for 790,000 people to be executed before he took charge, since its unlikely that the Germans would have access to Russian POWs before Barbarossa.
Calculating final precise figures for those who died in the holocaust may not be an exact science but I'm reasonably sure not even the Soviets would try to pull that kind of leap of numbers.
The wiki page:
http://en.wikipedia.org/wiki/Sachsenhausen_concentration_camp
This states the following on the total number of deaths:
About 200,000 people passed through Sachsenhausen between 1936 and 1945. Some 100,000 inmates died there from exhaustion, disease, malnutrition or pneumonia from the freezing winter cold. Many were executed or died as the result of brutal medical experimentation. According to an article published on December 13, 2001 in The New York Times, "In the early years of the war the SS practiced methods of mass killing there that were later used in the Nazi death camps. Of the roughly 30,000 wartime victims at Sachsenhausen, most were Russian prisoners of war, among them Joseph Stalin's eldest son (Yakov Dzhugashvili).
(also supported by other sites such as the Jewish Virtual Library).
Whichever figure you take neither are close to this 840,000 figure you mention.
So I suggest you find the transcript and post it here so that we can see exactly what's being said by whom and it what context.