Alt Calibration Question

When I calibrate the alitimeter on my Advizor, while I am scrolling from my current elevation reading to my actual elevation, sometimes I encounter the message "def" at a certain altitude setting. For example, if my watch says 2570 feet, and I calibrate to 2500 feet, the watch might display 2560, then 2550, then 2540, then 2530, then "def", then 2510, then 2500. What does "def" mean?

	Suunto Advizor - Click for more info The Suunto Advizor - featuring a Heart Rate Monitor using Suunto's proprietary HR technology - simultaneously shows your heart rate, altitude, and vertical ascent/descent data. The Advizor memory stores your total training time and your maximum, minimum and average heart rate during training - plus your time spent in / above / below your pre-set target heart rate. There's even an audible alarm to alert the user when your upper or lower heart rate limits have been exceeded.

[AltimeterGuy]

The default is more or less the factory setting to use if you are not at an accurate known altitude to set your Wristop.

AltimeterGuy