Smart Gwt does not show on Hover Values for stacked Graph

I had a test case where the data Values for stacked Graph are("Cost1", 160303),("Cost2", 234234),("Cost3",0.1)
chart.setShowValueOnHover(true). These values are for single stack in graph.

In the Graph shown values for Cost 1 is shown perfectly but I doesn't show values for other two Cost2, Cost3.
Note:Graph shown is perfect, the issue is with the on hover values.

This scenario is repeated when ever any one of the Cost is too low in comparision to the rest Costs. Please help for the solution

Thanks in Advance