Yes, that is the altitude.
For example: An automotive engine can lose 30 percent of its power just by driving to Denver, the Mile High City.
And if the MAF is not 100% working then, it will be even more.
http://www.2-stroke-porting.com/altiden.htm
Here is also a good info and explanation
http://www.moparchat.com/FORUMS/showthread.php?t=89022