Subdivisions of estimates of resources to be recovered by a project(s) to indicate the associated degrees of uncertainty.
Examples of Resource Categories used in PRMS 2018 are: Low/Best/High, P90/P50/P10, 1P/2P/3P, 1C/2C/3C, 1U/2U/3U.  It is represented by the horizontal axis of the PRMS Resource classification framework.