Stepping out to a clearer source, Wikipedia[1] summarizes data from the World Bank and the CIA. I think the numbers that best reflect current China suggest a 12% (CIA at birth), 17% (CIA 15 or younger) or 19% (WB at birth) disparity depending on the estimate. Choose any of those and you've got a pretty huge disparity. I think that the article may have been looking only at a cohort, not the entire population, so taking the ratio of the quoted number of missing men against the entire Chinese population may be misleading.

[1] https://en.wikipedia.org/wiki/List_of_countries_by_sex_ratio