“Note that if you choose a too important height for your letters, you’ill get multiple Font Texture Pages. This is not very harmful, but remember that only the characters in the first page will be displayed correctly when using this font. So you can ignore it if some few unused characters are banished in a second texture page, but get sure you have at least all of your letters in upper and lower case.”
You can hand select the fonts you want to use by typing them into the “Chars” section, that way you can make sure all the glyphs you want to use are on the first (and only) sheet.
This works even better if you only need a few letters, for instance the 6 that re used in the words RED and BLUE, as you can then make them much bigger and still fit on the sheet.