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with 1 being the standard deviation, 100 is the number of samples, 128 is the scaling factor of the sample size and finally 256 (twice the scaling factor) pushes the whole function to the right so that 1 >= x >= 512
In order to create a larger set of file sizes with a larger median file size you could use stdnormal_rnd(1,500) * 256) + 512. This will create 500 file size entries between 1 and 1024.
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