This is a modification that alters values of shadow cascade(s) for better performance.
In practice, what happens when using this mod is the terrain shadows (outside-cockpit) being drawn as far as before, but with overall performance improved with quite small visual difference trade-off. The other benefit is that, at the same time, the inside-cockpit shadows maintain high quality in all settings (4096x4096 pixels shadow, though even that can be changed if really desired).