This simple HTML file calculates the probability of a value from the shortened range it will occur.

I made this because due to the source RNG strictly being an integer ranging from 0 to 2ⁿ-1, it is possible that when you convert that range to a smaller range that doesn't have 2ⁿ possible values, you'll have a slight uneven distribution of numbers (some results happen more often than others). This is because the number of values don't evenly divide. This discrepancy is much larger the bigger the range you convert it to in relation to the RNG size. See this video as an example.