when to use bumpmap with low range?

i noticed Bertrand Benoit uses low range in his bumpmap,in his tutorial on materials
http://bertrand-benoit.com/blog/materialism-1/ .i am guessing when the bump effect is subtle you can put more details within a low range. i am attaching his bumpmap with a histogram added


so,what do you consider when making bumpmaps?

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