The arrows are the "highlight" "shadow" and "clipping" points. They are programmable.
You can use the default settings, they agree with a standard profile.
I programmed mine to fall on whole stops to agree with traditional "Zone System". I didn't have to move the points very far.
I use it in "shutter priority" mode where the f/stops display. I look at these arrows to place highlights or shadows. Spotmeter any single point, then look at the f/stop at the shadow point to get the setting to use. Since I moved the arrows, when I take the f/stop nearest the shadow arrow, I effectively place that spotmeter reading on Zone II.