This indicator displays the combined volume for all the exchanges listed in the settings menu.
For example, with the default settings, on BTCUSD the indicator will display the current market's volume AND the volume of all other major exchanges listed on TradingView.
The gray indicator value is the current exchange's volume, the colored volume is the combined volume of all other exchanges, allowing you to compare the current exchange's volume to the broad market to give you a better idea of local exchange activity versus broad market activity.
If you want to add more exchange tickers, turn "debug" mode on and a small label will appear in the top right telling you which market type & exchange ticker you're currently on. All exchange tickers must be separated by a comma.
The "Other Exchanges" input setting overrides all other lists allowing you to specify your own exchange list for assets not provided by the default settings (the indicator supports crypto, forex and stocks by default).