As Yetive said, run a ton of double shots and it'll tell you which way to turn the knob. Hitting the plus and minus signs at the same time will give you a ton of information and you can scroll down with the minus sign. Press clear to get out of it.
I was taught to think of it in larger terms to figure out which way to turn. If you pour water through sand, the water will take a while to go through and some will get absorbed into the sand. If you pour water through a bunch of tiny pebbles (very extreme example of coarse coffee), the water pretty much goes right through in no time.
This is great when trying to figure out which grind to use, especially when grinding something for a guest. With a cone shaped filter (pour overs), the water drops right through, so you need a fine grind to slow it down. With normal drip coffee, the water goes down, hits the bottom of the brew basket, and then has to go towards the center, so it takes a little bit longer and you need a medium grind. For a press or cold brew, you are allowing the water to sit in the coffee for a long time -it's not going through the grinds, it's drowning in there with them; you need a really really coarse grind so it doesn't get overextracted and taste terrible.
Fine coffee slows down the water. Coarse coffee speeds it up.