Excel conditional formatting added programmatically with VBA displays 15 decimal places?

In Excel 2016, I'm using VBA to add conditional formatting to certain cells, based on a lookup of target values.  Here's my code:

    thistarget = targets(whichyear, whichquarter, lookup)
    Set myrange = ActiveSheet.Cells(lookup, 4)
    myrange.FormatConditions.Delete
    With myrange
        'if less than or equal to target, color green
        .FormatConditions.Add xlCellValue, xlLessEqual, thistarget
        With .FormatConditions(1)
            .Interior.Color = RGB(146, 208, 80)
            .StopIfTrue = True
        End With
        'if greater than target up to 15% over, color amber
        .FormatConditions.Add xlCellValue, xlBetween, thistarget, (thistarget + 0.15)
        With .FormatConditions(2)
            .Interior.Color = RGB(255, 192, 0)
            .StopIfTrue = True
        End With
        'if more than 15% over target, color red
        .FormatConditions.Add xlCellValue, xlGreater, (thistarget + 0.15)
        With .FormatConditions(3)
            .Interior.Color = vbRed
            .StopIfTrue = True
        End With
    End With

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Note that thistarget is dimensioned as a "single" value.  I can stop the code after line 1 and verify that thistarget = 0.63.   So what I expect to see is this:
But what I actually see is this:
Functionally it works, but if anybody goes to look at the conditional formatting formulas they are going to think I'm nuts.  

Why is it giving me so many numbers after the decimal?  

By the way, if instead of using a variable I hardcode line 1 to say "thistarget = 0.63" then I get 2 digit precision as expected.