This is intended behavior.
For percentile values outside the range of data, "prctile" will output the minimum or maximum of the data as appropriate. In this case the "prctile" function was returning the minimum value in the data both times, because both .008 and .016 are outside the minimum percentile.
For more information about the algorithms involved in the "prctile" function, please view the following documentation, under the "Algorithms" section:
