scrollTop max scroll is lower than $(window).height()

why does my scrollTop max value is 3409 while the $(window).height() is 4400 what might be the problem?

$(window).scroll(function() {
   if($(window).scrollTop() + $(window).height() == $(document).height()) {
       console.log("bottom!");
   }
});

I've been following this but what I noticed is my $(window).height() and $(document).height() return the same value which is baby 4421 while my scrollTop() when scrolled to the lowest returns 3409.

what are the possible causes?