The sentencing recommendation is based on Federal Sentencing Guidelines (the article does note this). Also, the sentencing judge has latitude in deviating from the guidelines, either up or down. I would not be surprised if Judge Jackson goes up because Stone refused to follow her orders during trial. The prosecution can recommend time outside of the guidelines, but they have to justify that deviation, as does the judge.
Further proof that the Trump DOJ, under the leadership of William Barr, has absolutely NO independence from the administration, as it is supposed to.
And instead of tweeting that the prosecutors, who are doing their jobs, are asking for too much time, just pardon him and be done with it already.