The large number (600,800,1000,1100, etc) is the maximum frequency in Mhz
The LV, SV, IV stands for Low-Voltage, Standard-Voltage, or Increased-Voltage. Low-Voltage will improve battery life and lower the cpu temperature, but for some speeds may be too low to be stable. Increased voltage will improve stability for very high overclocks, but will decrease battery life and increase temperature.
Pick some combination of steps, max frequency, and voltage level and try it out. Grab a few of them and load them onto your SD card, and you can easily swap between them using ROM Manager or just Clockwork Recovery.