Overview
The fonts are built with an older, out-dated style resource called a "FONT" resource which can cause problem with some applications. 

Details
Modern fonts are built with a new resource type called an "NFNT" resource. It has been shown that the old style "FONT" resources can significantly slow down the performance of some Macintosh software applications. These older fonts should be converted to the newer "NFNT" resource type.

Solution
FontDoctor will update the old "FONT" resource types into newer "NFNT" resource types.