By “billion” they mean what they claim is “nearly a billion dollars worth of quasi-secret reports commissioned by the United States Congress.”
The 6,780 reports, current as of this month, comprise over 127,000 pages of material on some of the most contentious issues in the nation, from the U.S. relationship with Israel to the financial collapse. Nearly 2,300 of the reports were updated in the last 12 months, while the oldest report goes back to 1990. The release represents the total output of the Congressional Research Service (CRS) electronically available to Congressional offices. The CRS is Congress's analytical agency and has a budget in excess of $100M per year.
Although all CRS reports are legally in the public domain, they are quasi-secret because the CRS, as a matter of policy, makes the reports available only to members of Congress, Congressional committees and select sister agencies such as the GAO.
Members of Congress are free to selectively release CRS reports to the public but are only motivated to do so when they feel the results would assist them politically. Universally embarrassing reports are kept quiet.
Regardless of the dollar figure, these are valuable reports to have accessible.