From your question, it is not exactly clear as to what study you are talking about. I have included below a link to a study by the Bureau of Justice Statistics that concerns recidivism rates of prisoners who were released in 1994. This study was released in 2002, but since it does concern recidivism and prisoners from 1994, I will hope that it is the right study and answer on that basis.
In this study, the researchers looked at the various characteristics of prisoners who were released and the rates at which these prisoners became recidivists. There are a number of categories that are included and which can be seen as “categories of recidivism.” All of these categories have to do with which things had happened to a released prisoner within three years of the time that he or she was released from prison. The broadest category was for 1) released prisoners who had been rearrested at any time. The narrowest was for released prisoners who had 2) been returned to prison with or without a new prison sentence. In between those extremes were categories for released prisoners who had 3) been reconvicted and those who had been 4) reconvicted with a new sentence.
Thus, we can see that there were four categories of recidivism in this study.