The Federal debt and deficits

"A budget deficit or budget surplus is measured annually. Total government debt or national debt is the sum of budget deficits and budget surpluses over time."

- 30.3 Federal Deficits and the National Debt

Yeah, that's what I thought: add up the deficits to get the debt.

So how come when I add up the deficits they don't equal the debt?

If you try it, let me know how it works out.