how does blender mange light sources and light emitting materials?

trying to simulate physically correct environments especially at larger scales does work but for some reason I need to put in absurd numbers to get somewhat realistic results, like light sources set at literal trillions of watts, comparable to the total sunlight received by the earth, so how does blender physically manage light and specially light intensity when rendering? there must be something off

for context I'm trying to simulate the color shift due to viewing distance and absorption coefficient underwater, white the color is correct if the value is plugged in the color of the "principled" volume node, it begs the question what is the "color absorption" value for? how does the density affect the appearance in a physical way?