We have to be honest: if we say only 6,000,000 Jews and go from 1933-1945, we're not even looking beyond what we knew at one point in history. The moment that the Great Depression began, the Anti Semitism that a then-still-relatively-marginal group known as the Nazis began to gain a scarily-massive affect. Also, Stalin wanted to destroy particularly Jews in the gulags and otherwise within the USSR. So, quite technically, the Holocaust began on October 24, 1929 and didn't end until the gulags closed. Also, how many Holocaust survivors (including Jewish-American and other Jewish Allied soldiers, Navymen, etc.) died post liberation and post war due to illnesses and injuries that they sustained while they were held in the murder camps and/or fighting against the Axis of Evil?
That doesn't even touch, e.g.:
- The Jews who died and were left uncounted because they did not count as Jews by Rabbinical and/or Karaite standards (or even by their own standards).
- Unborn Jews who were miscarried and died in wombs, often with mothers whom knew of their pregnancies and were not spared the gas chambers, crematoriums, and other horrors despite their pleas for their babies to be saved.
- The Jews who died in hiding.