The Obama administration admitted today that it mistakenly inflated the number of health insurance enrollments under the Affordable Care Act by adding in those who selected dental plans to raise the total above 7 million — the White House’s original goal.

“This mistake is unacceptable,” Health and Human Services Secretary Sylvia Mathews Burwell said on her Twitter account today. “I will be communicating that clearly throughout the department.”

The mistake we made is unacceptable. I will be communicating that clearly throughout the dept. — Sylvia Burwell (@SecBurwell) November 20, 2014

Congressional investigators with the House Oversight and Government Reform Committee discovered the error after receiving data from the Centers for Medicare and Medicaid Services, a sub-agency within HHS that oversees the Affordable Care Act, popularly known as Obamacare.

The Obama administration incorrectly added 380,000 consumers who selected only dental plans, Bloomberg first reported. According to CMS, the accurate number of Americans who selected health insurance plans is 6.7 million.

In a prepared statement, House Oversight and Government Reform Chairman Darrell Issa said:

HHS must provide a clear and detailed account of who knew about this decision and when they knew it. This administration still appears to be calling its Obamacare transparency plan from the Jonathan Gruber playbook: dismissing the American public’s right to know with the same deceptive arrogance that helped them pass the bill in the first place.

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Since the first open enrollment period ended in mid-April, the administration’s reported enrollment figures have declined.

First, in May, the White House celebrated enrollments topping 8 million. However, that figure was disputed because HHS failed to distinguish between those who paid their first month’s premiums and those who did not. More than 1 million enrolled in dental coverage, the administration reported that month.

Then, in September, CMS Administrator Marilyn Tavenner told Congress that 7.3 million Americans had enrolled in health plans through the Affordable Care Act.

Last month, Tavenner said enrollment was around 7.1 million.

Ed Haislmaier, a health policy expert at The Heritage Foundation, noted the decline in enrollment figures throughout the first half of 2014. In a recent report, Haislmaier and Heritage colleague Drew Gonshorowski found that 6.5 million Americans enrolled in Obamacare, according to data provided by insurers.

“It’s another reason that explains why the actual insurer enrollment figures are lower than what HHS has been saying,” Haislmaier told The Daily Signal, adding:

It explains the discrepancy. Insurer enrollment data shows that the market increased by 6.5 million in the first half of 2014, so this helps explain the delta between that and [the] 7.1 million reported by the Obama administration.

In previous administration reports regarding enrollment, the numbers of who signed up for medical and dental plans were reported separately. The White House’s decision to combine the two in the total of 7.3 million broke from that practice.

“A mistake was made in calculating the number of individuals with effectuated marketplace enrollments,” CMS spokesman Aaron Albright said in a statement to The Daily Signal. “We have determined that individuals who had both marketplace medical and dental coverage were erroneously counted in our recent announcements.”

In the future, he said, only those with medical coverage would be included in enrollment numbers.

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According to The Washington Post, HHS reported higher enrollment figures twice. In September, the agency inflated the total by roughly 400,000. This month, HHS said 7.1 million were enrolled when 6.7 million actually were.

The Oversight Committee’s findings come just one week after the second Obamacare open enrollment period began.

The White House has been working to distance itself from Jonathan Gruber, a Massachusetts Institute of Technology economics professor who helped craft Obamacare, the president’s signature domestic achievement.

Videos recently surfaced of Gruber discussing how the White House and Senate Democrats manipulated the language of the health care law on purpose, passing it with a deliberate “lack of transparency.”

In subsequent videos, he called the American people “stupid” and mocked a man for expressing concerns about the effects of the law.