Your RAM isn't 1866 MHz, it's DDR3-1866 as in 1866 MT/s = 933 MHz. DDR3 has a Double Data Rate, so the number of memory transfers is twice the actual clock. Memory vendors like marketing their product with the larger number, and then "accidentally" having people confused and thinking it's the clock rate in MHz.
Your last screenshot says 936.2 MHz which would correspond to DDR3-1866.