The sentencing court did not erroneously exercise its discretion when it made Pokey, who was convicted of armed robbery of a bank, ineligible for the Earned Release Program. At sentencing the court based its decision on all of the required sentencing factors, not just on the seriousness of the offense, as Pokey contends. (¶¶4, 7-11). The court also properly denied Pokey’s postconviction motion to modify his sentence to make him eligible. The motion was not based on one of the recognized grounds for sentence modification–namely, a showing of a new factor; a determination that the original sentence is illegal or void; or a determination the sentence is unduly harsh or unconscionable. State v. Harbor, 2011 WI 28, ¶35 & n.8., 333 Wis. 2d 53, 797 N.W.2d 828.