My husband is appealing conspiracy case and was just sentenced to 15 years in federal prison, does he have any chance for less jail time?

My hysband was aressted one year and a half ago charges with conspiarcy they were then acusing him of being the leader of the organization although as time went by the prosecuter and dea agent found out that he was not a leader. And my husband acepted his role in being involved be not of being the leader and also was of some help to the dea agent he was still given 15 years he would like to know if their is a chance that he can appeal and get less time. He belevies that their was points not taken off that were given to him but at the end not given.