How much does the Debt Limit Deal save? It’s complicated.

A crucial question for the bipartisan debt limit deal is deceptively complicated: How much would it actually reduce federal spending?

The answer depends on whether you’re considering the whole deal — including side deals that aren’t in the bill — or just what’s technically in the bill. And the count grows or shrinks dramatically depending on what you think a future Congress will do on spending.

After factoring in all spending caps and related accounting tricks, The New York Times estimates that the deal will actually reduce discretionary spending by about $55 billion next year, compared to baseline projections, and by another $81 billion by 2025.

That’s the total savings: $136 billion, compared to what the government expected to spend over two years. Everything else is in motion.

Republicans claim a much higher overall cut: $2.1 trillion over a decade. That is based on one analysis of the agreement by the Congressional Budget Office. And it’s based on a lot of policy decisions that Republicans will follow for years to come. Most importantly, that number assumes Congress voting to introduce four years of optional, unenforceable spending limits following the two years of hard limits in 2024 and 2025. It’s possible, but the deal in no way requires that this happens.

The budget office also offered a share of the bill based only on the two enforceable years of limits. It found that the caps would save the government about $1.5 trillion in spending and interest on the debt over a ten-year period. However, most of those savings will come in the last eight years of the decade, after limits are lifted.

The budget office assumes that when the caps are gone, Congress will simply go back to essentially increasing spending in line with rising prices. So if you cut spending for a few years, as the caps do, then the spending goes down because it just starts growing again from a lower base. That’s a possible outcome for the next decade, but Congress could very well decide to go straight back to big spending increases — negating those expected savings.

So what about the two years when the limits are binding? The budget office finds significant savings there — about $250 billion in total for the two years. But even that number may be too high, as the analysis doesn’t account for the extra spend included in the side deals.

Factoring in that additional spending — using White House estimates of where they would leave discretionary spending levels in 2024 and 2025 — cuts the expected savings to about $136 billion. That’s probably the bottom of what the spending caps will translate to, in terms of spending cuts.