Relative Volume is displayed as a ratio. So if it is showing 3.5 relative volume, that means it is trading at 3.5 times its normal volume.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.