This is a very simple indicator. It plots the high timeframe (configurable via the "Timeframe" setting) high/low current timeframe bars (that has the same high/low as the higher timeframe) as supply/demand. The higher timeframe bar that's chosen is the one that's next last. As of now one high and one low zone is plotted.
The defaults are based on useful zones when on daily candles.
You can choose to display the higher timeframe within the zone via the "Show" option.