In relation to fonts sizes, we often use in-between sizes, such as 12.5, 13.5. These half-sizes are typed into the font size box. This helps greatly when, for instance, trying to compose a one-page letter, but finding that the letter extended out to a second page of just a line or two. Reducing the font size of the overall letter just a little, i.e. by 0.5, can reduce the type size just enough to bring the typed letter back to one page of text.