Just to help you understand it if you are having trouble, those numbers that they give you for timings are in clock pulses. Meaning it takes, say 7 clock pulses (at 1333Mhz) for that type of command. 7 clock pulses at 1300Mhz = 5.385 nanoseconds, which means the RAM needs 5.385 nanoseconds to do that type of command.
But a clock pulse at 1600Mhz is quicker than a clock pulse at 1333 Mhz. So for your RAM to have the required minimum of 5.385 nanoseconds to do that command at 1600 Mhz, 9 clock pulses will have to go by, because 8 clock pulses would only be 5 nanoseconds, which might not be enough time for the RAM to perform this task.






