So what IS the figure, and is it contested? I honestly have NO idea.
I don't know what the "true" figure is, but for JUST the Ukrainian S.S.R. victims during the first "Five-Year-Plan" (1928-1933), I've seen estimated death tolls ranging from 5 million (a number admitted by later Soviet historians) to 20 million (a number claimed by some Ukrainian nationalists living outside the USSR).

Different political biases aren't the only source of the disagreement. It's likely that millions of "unaccounted for" Ukrainians were geographically displaced by the "Первая пятилетка", but many did not die as a direct result of the Plan -- instead, they may have perished years later during the Nazi invasion (not as a result of being murdered by their own government).

Also, there were two serious droughts in Ukraine during this five-year period, which suggests that many would have died from famine anyway even if the Five-Year-Plan had not existed -- yet it's almost certainly the case that the Plan needlessly increased the total number of famine deaths. But what percentage of the deaths from starvation should be blamed on Stalin's policies, and what percentage were due to the "unavoidable natural disaster" of the two droughts? (In other words, if a famine occurs under conditions of a centrally-planned economy, should we conclude that the famine itself was "planned"?)

P.S. Of course, there are similar uncertainties when trying to estimate the total number of Chinese who died under Mao, or the "real" number of African victims during the centuries of the trans-Atlantic slave trade. (We don't know the total number who died IN AFRICA while being transported to the slave ships, for example.)