The Probcast legend is designed to be toggle-able, so you can turn legend members on and off.
This article will explain why this is useful, and how you can use the feature to help interpret incoming conditions.
The example below is a classic rainfall probability pattern in the summer. There is a heatwave and conditions are generally dry, but there is a small chance it could break out into very heavy rain.
In this graph, it is useful to see that there is a maximum simulation showing >10 mm/hr of rain on Tuesday night, creating a flash flood risk.
However, it is also useful to see what is more likely. The graph below shows the same forecast, but we have clicked the grey legend member (<2.5% chance) to turn them off.
In the updated graph the view is now clearer, and we can see that very heavy rain remains unlikely, with the expected outcome drizzle on Tuesday morning and a small chance of moderate-heavy showers.
Both views are useful, and given there is potential heavy rain in the forecast, it would be worth watching closely how that forecast evolves as Tuesday approaches.