Wonkblog's Sarah Kliff breaks down the policy you need to understand about the Affordable Care Act, from politics to premiums. (Video: Kate M. Tobey/(In Play))

As the Affordable Care Act's enrollment stage enters its 18th day of operation, we thought it would be worth considering a few numbers that highlight what parts of the system are working, and what aren't.

1. Two seconds. That's the average wait time at the federal marketplace's call centers, according to a senior administration official who asked not to be identified because the wait time varies depending on the time of day. Many Americans are now calling in to sign up for insurance rather than rely on the official government Web site, HealthCare.gov.

2.  17 million. That's how many unique visitors have come to HealthCare.gov in its first two weeks, according to Health and Human Services spokeswoman Joanne Peters. That's a clear increase from the first three days, when 8.6 million unique visitors logged on to check it out.

3. 88 percent. That's how much traffic on HealthCare.gov dipped between Oct. 1 and Oct. 13, according to an analysis  Millward Brown Digital prepared for U.S. Kantar Insight this week. The estimate is based on the online use of 2 million American households, tens of thousands of which logged onto the site. The Obama administration challenges that estimate, though it has not provided a daily breakdown of visits to the site.

4. Two. That's how many House panels are formally investigating the health-care law's implementation. The House Oversight and Government Reform Committee held one hearing last week and is continuing to probe the issue; the House Energy and Commerce Committee has scheduled one for Oct. 24. In addition, Sen. Lamar Alexander (R-Tenn.) joined Oversight and Government Reform Committee Chairman Darrell Issa (R-Calif.) in sending a letter to HHS Secretary Kathleen Sebelius Oct. 10 demanding that she explain the technical problems facing the Web site, outline what the administration was doing to fix them and detail what the administration knew about them in advance.

5. Three. That's the number of Republican senators who have pledged to continue fighting to block the Affordable Care Act through whatever means necessary: Ted Cruz (Tex.), Marco Rubio (Fla.) and David Vitter (La.).

6. Four. The number of states — Arizona, Florida, Tennessee and Texas — where Cigna, a major insurance carrier, has told its agents not to try signing up customers who might qualify for a federal subsidy until November. Cigna made the decision after receiving multiple enrollment forms from individual consumers on the same day using the federal Web site.

7. 10 percent. That's how much Oregon has been able to reduce its uninsured rate in two weeks by enrolling people through a fast-track process under a low-income, Medicaid-funded program. Oregon has its own insurance marketplace rather than the federal one.

8. 27 percent. The portion of respondents in a recent Washington Post/ABC News poll who thought it was right to shut down the federal government over Obamacare.