If operating on the Western Rivers System, what do numbers fixed below Day Markers indicate?

When operating on the Western Rivers System, numbers that are fixed below Day Markers indicate the distance to the river mouth. These markings are crucial for navigation, as they provide boaters with a clear understanding of how far they are from significant points of interest, such as where the river meets a larger body of water.

This information helps boaters plan their journeys, ensuring they have enough time and resources to reach their destination safely. Understanding these markers is vital for maintaining awareness of your location within the river system, which can be particularly challenging given the shifting currents and varied water levels typical in these waterways.

While the other options regard different aspects of navigation and safety, they do not correctly apply to the fixed numbers found below Day Markers, which serve primarily to inform operators of their distance from critical points on the river.