Guaranteed stop loss is a stop loss that acts as your insurance against disastrous losses or any gaps in the instrument that you are currently trading. It allows you to close a trade at a specific price you have set without incurring major losses.
The guaranteed stop loss fee is calculated by multiplying 3 components: guaranteed stop premium (in percentage), position open price and quantity. The formula looks like:
GSL fee = GSL premium * position open price * quantity.
You can check the GSL fee value in a deal ticket when opening a position and adding GSL.