Thx for the reply. It does look like a stacked graph but a few things odd:
1) It says Upload on one side and download on the other. But as the 2 lines follow each other, it can't be both.
2) If it was just the same graph repeated, they should be exactly on top of each other, but one is slightly less than the other (in 4 out of 4 example sites I have looked at). So is it just a glitch, or is on graph showing, I don't know say download minus management overhead or something?