Set a simple buy-low / sell-high rule against a whole year of real New South Wales electricity prices (2024), and see how close it gets to the best possible result.
Perfect foresight is the most any rule could earn if it knew every future price. No real operator does, so the gap between your rule and that ceiling is the value of knowing the future. And even the ceiling is an over-estimate, because a 2,200 MW plant would push prices against itself — it is not really a price taker.
Note. These two sliders are yours to tune to 2024. The report's rule of thumb instead freezes its triggers on 2022 to 2024 and applies them unchanged to a held-out year, so it can be judged out of sample. Here you are exploring the family that rule is chosen from, not the frozen rule itself.