All @RISK distributions support two additional parameters, TruncMin and TruncMax, collectively called "truncation limits". These values limit the range of a distribution. For example, if you have something normally distributed which you do not want to sample below zero, you could set a TruncMin value of zero.
If you are using RISK functions to sample a distribution, the truncation limits are two an additional optional arguments to the function. If you are sampling from an RDKDistribution object, use the TruncMin and TruncMax properties to set the truncation limits.