The Simpson-Bowles commission recommended that the federal government undertake $4 trillion in debt reduction. So did President Barack Obama. Obama's advocates want to make it appear that the two $4 trillion figures are equivalent."He has offered a reasonable plan of $4 trillion in debt reduction over a decade," former President Bill Clinton said last week in his Democratic convention speech. "That's the kind of balanced approach proposed by the Simpson-Bowles commission, a bipartisan commission.""He put forward a budget …that would get to the $4 trillion goal that came from Bowles-Simpson," Obama economic adviser Austan Goolsbee said on Fox News Sunday.Not exactly. First of all, the Simpson-Bowles plan envisioned $4 trillion in debt reduction over nine years; the president's plan would spread the cuts over 10 years — a difference that matters because the value of the savings piles up at the end of the window. For instance, the Simpson-Bowles report shows $817 billion in deficit reduction in 2020 alone. Another year makes a huge difference.Second, Simpson-Bowles assumed the expiration of the Bush tax cuts for the wealthiest Americans before laying out its $4 trillion in reductions. In budget-speak, that was built into the base line. The Obama plan counts as "savings" allowing the top-end Bush tax cuts to expire ($849 billion from 2013 to 2022) along with keeping the estate tax at its 2009 level ($119 billion over the same 10 years). Again, another huge difference.Lastly, Simpson-Bowles assumed lower spending on the wars in Iraq and Afghanistan. The president's plan pads his debt reduction with "savings" in comparison to the wars continuing at the same pace for a decade. This amounts to an $800 billion difference.When the president released his budget in February, the Committee for a Responsible Federal Budget assessed its savings to be "far below those" of Simpson-Bowles. After aligning assumptions, the nonpartisan committee found Obama's $4.3 trillion to be comparable to $6.6 trillion of Simpson-Bowles savings. That's a difference of $2.3 trillion, or more than 50 percent.The best measure of whether the country is on a sustainable fiscal path is where federal debt would stand as a share of gross domestic product. At the end of a decade, the Obama plan would have debt at an unhealthy 76 percent of GDP, according to the Congressional Budget Office. The comparable ratio from Simpson-Bowles: 69 percent, still high but less troubling. At least as important, the president's plan would leave the debt stuck at that level. Simpson-Bowles would put it on a downward path.Obama can claim to have outlined an initial plan to tackle the debt, one that follows the Simpson-Bowles approach of combining revenue increases with spending cuts. He can claim that his plan, unlike Mitt Romney's, has detailed proposals behind the numbers. He can claim to have achieved $1 trillion of the promised savings already, through spending cuts.But Obama cannot claim to be seeking anywhere near as much in debt reduction as his appointed commission said was needed to preserve the nation's fiscal health.