smoothMoveTo and moveTo move dom to different place with same x y

[SLEEPYkoa1a]

When I use moveTo and smoothMoveTo before smoothZoom, like
panZoomInstance.moveTo(60, 60);
panZoomInstance.smoothZoom(30, 30, 1/2);
and
panZoomInstance.smoothMoveTo(60, 60);
panZoomInstance.smoothZoom(30, 30, 1/2);
the dom will stop at different place, and moveTo reach the right place I expected. Looks like something wrong happended in smoothMoveTo method.
Is there someone has the same question?