I think you might have a misunderstanding about how tax brackets work (at least if you’re taking about american federal income taxes). Progressive tax rates mean that only the income that is over the threshold for the new tax bracket gets taxes with the higher %. So if you are $1 over the limlt for a new tax bracket, only that dollar gets taxed with the higher percentage. You can read about this anywhere, this is just the first source I found.
So, I don’t see how this example still applies here. But after some reading, apparently the prosecution got some new information after the plea deal, so the asked for 9 years, and the judge compromised on 8.5. That’s at least what this article implies.
Pazienza’s plea agreement called for an eight-year sentence but prosecutors asked for nine years based on new information contained in a presentence report, a spokesperson for Manhattan District Attorney Alvin Bragg said.