It all depends on the settings of your project.
For example, the DIALOGUE_WIDTH should match your game's window size or be a little smaller, depending on your need and the coordinates you used to position the dialogue window.
If your game's window size is very small, a DIALOGUE_MARGIN of 16 is probably too much and you should adjust it accordingly. For best results, it should match your 9-patch window object's margin size.
You can't really break anything unless you use absurd values that makes no sense, so don't be afraid to experiment a bit.