The built-in batteries in the newer Mac unibody notebooks come pre-calibrated and
do not require regular calibration like the removable batteries in older Apple notebooks. Simply draining and recharging is not calibration.
It is perfectly normal if your battery health (maximum capacity) is more or less than 100%, even when brand new, or if it fluctuates up or down over time. The gradual decline is not in a straight line downward, and it may decline more rapidly at some times and slower at others. For further details, read the CHECKING STATUS AND HEALTH section of the FAQ posted earlier.