The agency specified that employers could still fall under the mandate if they employ enough part-time workers to equal 50 full-time workers. For example, if an employer has 40 full-time workers and 20 part-time workers, that employer would be considered by the government to have 50 full-time workers and would be subject to the mandate because the 20 part-time workers average to 10 full-time workers – meeting the 50 full-time-worker threshold.
http://cnsnews.com/news/article/irs-warns-employers-do-not-try-avoid-obamacare-insurance-mandate
Thanks for the explanation and the link to the article.