You did not say what speed chips you put in, but whatever it is, it is running at 533 Mhz which is valid for DDR2. Others are 667 and 800Mhz. If you have different speed chips installed together, they will default to the lowest one.
If you installed say three 800 Mhz chips and it is reading as 533, then your motherboard is likely set to run the ram at that speed. It won't really hurt anything, and you will really not notice in most applications.
Without more info about the ram or system, I cannot really help further.