Video card software lying?

Question

GPGPU

GRU-Z shows that the video memory frequency instead of 4000 MHz is only 1000 MHz. I read on the forums that you need to multiply by 4 or 3 and you will get your frequency, but I never received a specific answer.
Who is not too lazy, explain to the young one :) Otherwise, I don’t understand why I need to multiply this, what kind of flows go there and where.

• Another micro question
  

regarding the type of video memory. Write how much you have to multiply by DDR3, DDR4, DDR5.