Click on the gear settings icon and type in your entry price. The percentage is defaulted to 5%. You can change this to a different percentage at this screen. Note that whatever number you enter will be doubled for the upper and lower lines. For instance, if you want to set your first red line stop loss and green gain line at 2.5%, your two other upper and lower green and red lines will be at 5%.
However, this will not change the text on the tab marker.
To change the tab text, go in to the Pine Editor and change the green text that says "5% Gain" and "5% Loss" to your new percentages.
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.