This applies only if your application uses Windows-style edit boxes for editing data fields. If so, they will normally use the standard Windows proportional font for the data characters. Some people don’t like the fact that this makes it difficult to see what is the maximum number of characters for a field. (With fixed pitch characters, the field size relates exactly to the number of characters allowed, but with proportional fonts, it depends on the widths of the individual characters.) One way to minimize (but not totally eliminate) that confusion is to set this option, which will force the edit boxes to use a fixed pitch font. The actual font will be scaled so that the maximum number of characters allowed will approximately fill the field space, but due to the idiosyncrasies of font scaling, it will never be quite as exact as it is with fixed pitch. (You may be able to set a switch in your application to get it to use the old-fashioned text-oriented input style rather than Windows-style; "Neo-Luddites" should contact their application developer for details.)