I assume you are talking about the memory clock speed.
So, as an example, on the RTX2080 Super page it says:
Memory Clock 1937 MHz
15496 MHz effective
That means the real clock speed of the memory is 1937 MHz. However, because DDR6 is capable of doing 8 operations per clock cycle, it provides the bandwidth like it was clocked at 15496 MHz. So it's clock speed is effectively 15496 MHz even though it is actually 1937 MHz.