Hi @tstone
Yes sampled uniformly in that range. For future reference in the parameterization class you’ll fine the sample function which calls the _sample_ranges function for each variable which is indeed uniformly sampling. Unless of course you choose quasirandom sampling or provide a discrete list / fixed value/ etc.
For fixed time-steps you could replace that tuple with a numpy array and it will select a value from the given array. Have a look at this source code here to see what happens for a given input. Hope this helps!