Need help with memory frequency and NB frequency

[HELLOYURI]

Hey guys.

I just built a computer for the very first time and I'm new to this whole thing. I have a Corsair Vengeance 2x4GB and it says in the box it's 1600MHz, but I noticed it was running at 1333MHz. I went on BIOS and set the memory to run at 1600MHz, I also enabled XMP. After that, I noticed the NB frequency increased drastically to 3999.1 MHz. I don't really know what that is, but I need to make sure everything is running safely.

My motherboard is an Asus Z97-PRO and my CPU is an i7 4790K.

Thank you in advance and sorry for the bad english lol.

 

[HELLOYURI]

Guys, does anyone know the answer? I'm a little bit concerned because I don't really know much about it and I need to make sure I'm not messing up my components.