Thanks for the info - that's kinda what I was thinking too.
Also, any idea why I can set all these parameters to negative numbers like -13?
If you are talking about script parameters, they are just numbers to be passed to the script. What ranges are valid are determined by the individual script, and CHDK doesn't know anything about this.
Even in CHDK menus, you should not assume that a value makes sense just because you can enter it.