>>989358H & L? What the fuck?
Regardless, what's to understand? One changes the gears from large to small in the front, and the other in the back?
You might want to downshift coming up a hill so it's easier to turn the pedal; because while you're getting less power out of that downshift, you're keeping the momentum of the pedal, which can be more important at this point. (Rather than keep that higher power output in a higher gear, but be unable to complete a pedal.)
You should be able to pretty much feel out whatever gear you need to be in, senpai.
