Why does my monitor have so many (360) supported resolutions?

I looked through the whole list and see about 20 unique different resolutions, the other 300 some are duplicated. I do have 3 monitors connected (All 16:9), knowing that, it shouldn’t print more than 60.

How can I get a short list of supported resolutions for only one of the monitors?

Resolution[] resolutions = Screen.resolutions;
print(resolutions.Length);
foreach (Resolution res in resolutions) {
        print(res.width + "x" + res.height);
}

If you take a look at Resolution, you may notice there is also a refreshRate field. In a brief test, I changed a line to:

Debug.Log(res.width + "x" + res.height + ": " + res.refreshRate);

… and found that, while the refreshRate field didn’t appear to update accurately for me (Unity 5.5.0f3: all entries were an unidentifiable 56), it did, however, reflect the number of variations of refresh rates which were available per resolution for my monitor.