As you "next" through the calibration tool, you'll get to a screen called brightness with a couple eyeballs and a grayscale ramp down the right hand side of the screen, with a couple white ticks marking either end. That gradient should be smooth throughout between the ticks. That ramp has both a smooth gradient side on the right, and avg by region on the left. Pay attention to the blacks up top. The brightness should change by the same amount between each region. If you see sort of a sharp divide in the smooth gradient where it goes from grey to black very quickly, then your gamma is too low. You also don't want it too be too dark all the way down the screen, gamma too high. Light intensity should vary by equal amounts in each region. After you have that correct, the adjust your brightness control going to the notch which just causes the top eyeball to disappear. You might need to readjust after setting contrast and find what you like best, but the most important thing is getting gamma to ramp correctly.
