I have found relatives who are listed two or three times, and other people I know from the Jewish Genealogy Society I belong to have found their own relatives there more than once. Almost always there are minor variations in spelling of the first and/or last names. Sometimes the given name is listed in one entry in Hebrew and another in the deceased's native language--Polish, Russian, etc. It doesn't change the tragically high number of Jews who were murdered, but it does call into question the validity of the number counted in Yad Vashem records.
Israeli army lifts closure on West Bank town of Qabatiyah after three days (Haaretz)
from the article: Holocaust facts: Where does the figure of 6 million victims come from?