This script is more like a tool than an indicator. The script determinates the amount of contracts and the leverage needed to do one trade.
You must specify the following parameters:
Entry price
Stop Loss price
Stop Loss risk. It's the capital that you will loss if the price hit the SL price.
Operation equity. It's the whole capital involved in the operation.
No matter what side of operation is, it works in both ways (short and long). To determine the levels could be useful use the short-long position tool of TradingView.