ok cool, looks good. The reason it shows 798 mhz, is because the CPU throttles its clock speed down when it isnt being used much. ANd that CPU-Z image is from a different site. Its on google images aswell, see here- http://hexus.net/tech/news/cpu/84626-intel-core-i7-6700k-skylake-flagship-cpu-benchmarks-surface/
Do me a favour, ask him wether thats his own cpu-z screenshot or if its one from google images. see what he says.