James,
.3C stands for 30% of the Capacity of the battery.
In your case, .3 * 1600 = 480 mAh or rounded up to 500.
When discharging I go to .9 volts per cell.
This fully discharges the battery and gives a better indication of what is happening.
When flying I stop at 1.1 volts per cell.
Here is a great website to learn more about batteries.
http://www.hangtimes.com/redsbatteryclinic.html
Good Luck,
KW_Counter