Please consider following limitations:
1. Maximum of 500 drawing objects per chart
To make sure the most relevant levels are shown, values are sorted based on the latest close value before levels > 500 are cut off.
2. Lookback history
The max lookback history is limited by the currently selected timeframe. E.g. on a 5min timeframe, 20000 bars (Premium Plan) result in approx. 5 months of lookback period, meaning you may want to have a 30 min or higher chart open to get a complete picture of levels, while trading on a lower timeframe.
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.