The only thing he could mean is the companies they invested in/bought created 100,000 jobs. Weren’t there over 100 companies? How much of a percentage increase above the previous employment? He very well cold be telling the truth, but it could be a meaningless statistic.
(Romney spokesman) Fehrnstrom says the 100,000 figure stems from the growth in jobs from three companies that Romney helped to start or grow while at Bain Capital: Staples (a gain of 89,000 jobs), The Sports Authority (15,000 jobs), and Domino’s (7,900 jobs).
http://www.washingtonpost.com/blogs/fact-checker/post/romney-vs-obama-on-job-creation/2012/01/03/gIQA31g3YP_blog.html
The 100k figure ignores job LOSSES at other companies, so it is a meaningless half-truth.