Typically, a parole matrix is composed of a risk category, an offense severity category, and the amount of time to be served prior to parole. Where the risk category and the offense category intersect, the matrix indicates the amount of time to be served by an inmate in those categories. Oklahoma's parole matrix consists of three levels of risk (high, medium, and low) listed horizontally and four offense categories listed vertically. Twelve intersections result, and each contains three numbers. The top number represents the median time served by a sample of inmates of that offense category and risk level prior to receiving a parole recommendation. The remaining two numbers represent the range of time within which aggravating or mitigating circumstances may be applied to modify the duration of time to be served prior to parole. Presumptive parole dates (PPD's) are assigned to most inmates based upon this matrix. The month and year of parole consideration are set at 2 months prior to the PPD. Exceptions to the matrix guidelines are explored, and factors considered by the parole board are examined.