Bug or bad hands in stacked graph?

[Roman Milovsky]

Hello! 

At the image is indicated by a red spot position of the mouse pointer. Blue graph has a value of 5000, but shows the value of green - 7416.7. If I move mouse up to 8000, then do not get any value. 

But if I depart right on graph (for example, last column) and bring on the blue, then get to 5000 and, if I move mouse lower to 0, I got the value of green graphics.