Am I reading this graph incorrectly?

http://img.photobucket.com/albums/v1...ofileChart.jpg

At the 45% power setting, the best range for a Cessna 150M would be
achieved by flying anywhere from sea level to a maximum of 1,800 feet?

At 75% power the gain is about 2.5 NM of range by flying at 7,000 feet vs.
1,000 feet.

This pretty much trashes my fundamental belief that higher altitudes give
greater range. What am I missing?



--
Dallas