The Congressional Budget Office (CBO) expects health care sign-ups in the state and federal exchanges during the open enrollment period starting Nov. 15 to total about 13 million people, but Health and Human Services (HHS) officials said Monday they expect only 9 to 10 million to sign up, including 6 million or so who renew.

The CBO anticipates a steady climb in enrollments during the first three years, topping off at about 25 million people. HHS officials say the process will take longer, maybe even five years or more.

Noting that open enrollment this year lasts just three months and not six as it did in the inaugural year, HHS Secretary Sylvia Mathew Burwell said, “We do have a shorter period of time and we are moving to a group of folks who may be harder to reach.”

There are currently about 7 million Americans enrolled in Obamacare policies.