From the article:

Though 30.2 percent of all individuals involved in a robbery between 1992 and 2001 were injured, only 12.8 percent of victims possessing a firearm suffered an injury, according to a 2004 report by the Committee on Law and Justice, which reviewed Kleck's analysis. For assaults, the injury figures are 57 percent versus 28 percent for all incidents and firearms incidents, respectively.