Look really closely at the numbers on the Y axis, For almost any x plot range it is cutting off a vast part of the bottom of the graph where it doesn't think anything "interesting" is happening and the curve then sometimes dips slightly below where they draw the x axis (at about y=7936.5)
Or add AxesOrigin->{0,0} as an option to your Plot.
Note to support staff. It would be really nice if during composing a reply a little note would pop up with "New Message Arrived" when someone else had submitted a response while you were responding to the same item. Gmail does that I think and some other mailers do to. That would allow hitting Cancel instead of Publish. Either that or a delete button to use on my previous post. Thanks for all your work.