I think they usually mean "much lower black and hispanic representation than demographics would suggest". The population of the USA is 13% black and 17% hispanic [0] - Microsoft employees are 4% black and 5% hispanic. [1] The coincidentally similar percentage of white people in the two groups is because MS has a far higher representation of Asians than the general population.

[0] - http://quickfacts.census.gov/qfd/states/00000.html [1] - http://www.microsoft.com/en-us/diversity/inside-microsoft/de...