"pixel"
PS: And here's how to find out such things: unzip all Kindle jars into a common directory.
This way, you can do string searches on classes:
Code:
LANG=C grep -r Font-Size-Mode java/classes
Binary file java/classes/com/amazon/kindle/kindlet/internal/install/j.class matches
Then you can open that class using your favorite decompiler (I use jadclipse) and simply click your way through to com.amazon.kindle.kindlet.ui.FontSizeMode, where you find these constants:
Code:
public static final FontSizeMode FONT_SIZE_POINT_MODE = new FontSizeMode("point");
public static final FontSizeMode FONT_SIZE_PIXEL_MODE = new FontSizeMode("pixel");