About 1.1 million Americans picked a plan through the federally run health insurance exchange as of Dec. 24 as part of President Obama's health care program, the Centers for Medicare and Medicaid Services announced Sunday.

But the announcement, which came in the form of a blog post from CMS administrator Marilyn Tavenner, left many key questions unanswered.

To start, the figure doesn't reveal how many people actually paid for health plans as of Dec. 24. Though payment is what typically makes enrollment official, up to this point, CMS has counted people as being "enrolled" if they merely went through the process of picking a health care plan.

Additionally, CMS still hasn't provided a demographic breakdown of those who have signed up for insurance through the exchange, which is a key metric for measuring the success of Obamacare, because the exchanges need a critical mass of young and healthy individuals to offset the cost of covering older and sicker enrollees and those with pre-existing conditions.

It's also true that the 1.1 million number (which represents a surge of 975,000 signups in December) does not include any signups from those states running their own exchanges  14, plus the District of Columbia.

But for context, it's also worth keeping in mind that before the exchanges opened, the Obama administration had projected 3.3 million enrollees by the end of December and the Congressional Budget Office had projected 7 million enrollments by March 31  the scheduled end of the open enrollment period.