Firefox setTimeout(func, ms) sending default parameters to callback

Question

I am unable to find out more about this default parameter that I ran across and was hoping that someone could point out an explanation.

In Firefox (3.6 in this case) if

Answer 1

You're correct that it's the offset. It'll usually be zero (meaning it was called when it should have been), but if the JS engine is backed up, it'll be higher, or it can even be negative.

reference: https://developer.mozilla.org/en/DOM/window.setTimeout

(see the part in yellow)