I've found the lower the value the better for reducing eyestrain. Slowly lowering it down in about 100K chunks it doesn't take long to get used to each step. I currently have mine at 4900/4200 (day/night).
Why so high at night? I do fine with candle setting at 1900K (though I turn my brightness up a notch from lowest).
The night value hasn't bothered me so I haven't given it much thought. I set it to that value when I first started using it as lower just looked weird at that time. I should probably try lower values at night and see if it effects my sleep.
My low setting makes me feel old. 3800 day / 2800 night. However, this is redshift (Linux), not sure it translates 1 to 1.