Question Ram dsnt Run Properly

[Barabaouras]

i have 4 x 8 GB of 3000mhz g.skill
when im trying to enable xmp, computer not starting up, even if i did it with "memory try it"
in advance mode says i have 2666mhz ram, and in windows shows the half of the half (667)

which is aut

 

[Barabaouras]

Well i tested all the sticks one by one, and by pairs, three of em works fine, and with xmp, the forth one not, not even booting when i have it alone on any dimm, but when i put it with another, lowering mhz to 1333... I guess i have to replace it.
But why in the bios and in windows shows up? And also calculated total 32gb?