The indicator will look at the last 20x, 50x candles (user defined setting) and take the highest volume value in this period.
It will then mark a solid line against the volume, calculated by a user defined variable percentage (default 16%).
If you determine any volume values that are under 16% (for example) of the highest volume candles in any given period, this indicator will paint this 16% level onto a volume chart for you, this is useful to quickly and conveniently see which candles held a volume below this level