After trumpeting "over eight million" enrollments just a few months ago in the exchanges for the Obama health law, a top Obama Administration official told Congress on Thursday that the latest report on the number of Americans signed up has shrunk by as much as 10 percent.

"As of August 15 of this year, we have 7.3 million Americans enrolled in the health insurance marketplace coverage," said Marilyn Tavenner, who heads up administration of the Obama health law.

At a hearing of the House Oversight Committee, Tavenner argued that smaller figure was not a disappointment.

"I think 7.3 (million) is a really strong number," Tavenner said, defending the Obama health law.

But the numbers are clear - 7.3 million is definitely smaller than the numbers given out by the Obama Administration after the end of the 2014 open enrollment session, which said "over eight million Americans have selected a private health insurance plan through the Marketplace."

That would mean the exchange rolls have shrunk by at least 700,000 in recent months, if not more.

"How much of that 700,000-plus drop were people who did not pay, or do you know?" asked Rep. Darrell Issa (R-CA).

"I do not know that information," Tavenner said. "I don't think we'll know that until the end of the year."

Those numbers could decline even more, because 115,000 people might be booted off the rolls at the end of September due to questions about whether they were citizens or legal residents in the U.S.

Tavenner later told lawmakers that she thinks the payment rate for those who signed up in the health exchanges would be about 90 percent.

Tavenner's press officials meanwhile downplayed the decline, telling reporters it's normal.

"The Marketplace is a dynamic place – people come in and out – even during the course of a year."

In a phone call, a spokesman from the Department of Health and Human Services disputed the headline of this story, arguing that one cannot compare the over 8 million enrollments and the August 15 snapshot of 7.3 million in the exchanges, saying it is not an apples to apples comparison.

The Obama Administration argues that some of the people who left the exchanges could have taken a job that has health insurance, so they wouldn't need to be on the exchange - they could have had another life change which placed them on another insurance policy, or maybe even cycled into Medicare or Medicaid.  But no numbers were available for those examples.

Officials also had no concrete numbers to offer on how many people may have been pushed off the coverage rolls because they did not pay their premium.

On the other hand, there would be the chance for people to sign up on the exchanges because of a life-changing event - they lost a job, their employer stopped providing medical coverage, etc.  So the ebb and flow can go both ways.