PROC HPSPLIT treats nominal variable values that do not occur in the input data set (either in the validation or in the training set) as missing values in the generated SAS DATA step scoring code.
PROC HPSPLIT assigns interval variable values that are outside the minimum and maximum range in the input data (the training and validation sets together) to either of the end bins. PROC HPSPLIT assigns a value that is less than the minimum to the first bin and a value that is greater than the maximum to the last bin.