PlotLegends in ListContourPlot for triplet of data showing strange numbers

Question

I am taking here just a modified example from the Mathematica documentation of ListContourPlot, because I have in principle the same problem:

data = Table[{x = RandomReal[{-2, 2}], y = RandomReal[{-2, 2}], 
    Sin[x y]}, {1000}];

ListContourPlot[data, 
 PlotLegends -> 
  Placed[BarLegend[Automatic, LegendMargins -> {{0, 0}, {10, 5}}, 
    LegendLabel -> "z-value", 
    LabelStyle -> {Italic, FontFamily -> "Helvetica"}], Above], 
 ImageSize -> Medium]

I get the following:

Making the legend image size bigger, one can see some numbers at the left hand side.

I am using Mathematica 9 and I really don't know how to remove that, I have tried everything.

I am aware of more advanced and customizable solutions like:this

But I really just want to do something simple and fast and don't want to start with that approach.