It's not uncommon for the SPD to be set a little looser than the fastest timing capable. This ensures maximum compatibility with various motherboard makers. Some makers like Corsair used to advertise that their SPDs were set to the correct timings so didn't have to do it manually. It's not a big deal though, just go into your bios and change it manually.
You won't usually have to adjust your voltage unless your having stability issues or overclocking. Just leave the voltage set at whatever it is now and tighten up the timings. If it is unstable then up the voltage a little.