first off, the SPD tab is what the memory is programmed as. it is perfectly normal to see PC2-6400 on PC2-8500 memory. JEDEC only has standards for up to PC2-6400 so that is what manufacturers should list in that window at the top. below is the SPD column of the actual profile which is what your memory is spec'd to run. take a look at a few SPD tabs of recent kits i have worked with:
Crucial Ballistix PC3-12800...listed as PC3-8500:
Corsair Dominator PC3-14400...listed as PC3-10700:
all the DDR2 kits from PC2-8500 up to PC2-9600 are also listed as PC2-6400, see my
Buffalo Firestix for the screenshots there. it is completely normal and you didn't get 'ripped off'.
now, to find out what your memory is actually running at so we can see if you are fully utilizing it, you need to look at the Memory tab of CPU-Z, not the SPD tab. HTH