YOU NEED TO SET THE MEASUREMENT SYSTEM TO "METRIC"
click Settings, then International and then "Metric - Altimeter in Meters"

This M U S T be done, or the altimeter won't show the altitude correctly: if you're thinking about leaving it set to U.S. system to get the altitude in feet, well that won't work: if the measurement system isn't set to Metric (Altimeter in Meters) the altimeter will show the wrong altitude, that's all. So, Set it to Metric and enjoy the flight.